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Page 1: Linear Referencing in ArcGIS - Esridownloads2.esri.com/.../707Linear_Referencing_in_ArcGIS.pdfLinear Referencing in ArcGIS GIS by ESRI Linear referencing in the ESRI® ArcGIS Desktop

Lin

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ArcGIS™ 8

Linear Referencing in ArcGIS™

$14.9592306

xxxx10/02spPrinted in USA

Linear Referencing in ArcGIS™

GIS by ESRI ™

Linear referencing in the ESRI® ArcGIS™ Desktop products suite—ArcView®, ArcEditor™, and ArcInfo™—enables users to create, manage,

display, query, and analyze data whose relative position has been modeled along a linear feature. Linear referencing in ArcView allows

users to display and query route and event data. Linear referencing in ArcEditor and ArcInfo supports creation and editing of route data.

Linear referencing in ArcInfo provides a variety of event geoprocessing operations that allow event data to be spatially analyzed.

You will learn how to

• Create route data from existing line data.

• Calibrate routes with points.

• Migrate existing route data to a geodatabase.

• Display hatches on linear features.

• Find and identify route locations.

• Display route events (dynamic segmentation).

• Edit route and event data.

• Perform a variety of geoprocessing operations with event data (overlay events, transform events, and so on).

Begin by following the quick-start tutorial to get an overview of how to execute the basic linear referencing functions. If you prefer, jump

right in and experiment on your own. When you have questions, you will find concise, step-by-step answers inside, fully illustrated, to

help you complete a task.

ESRI • 380 New York Street • Redlands, CA 92373-8100 • USA909-793-2853 • FAX 909-793-5953 • www.esri.com

ISBN 1-58948-063-5

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Copyright © 2002 ESRIAll rights reserved.Printed in the United States of America.

The information contained in this document is the exclusive property of ESRI. This work is protected under United States copyright law and otherinternational copyright treaties and conventions. No part of this work may be reproduced or transmitted in any form or by any means, electronic ormechanical, including photocopying and recording, or by any information storage or retrieval system, except as expressly permitted in writing by ESRI. Allrequests should be sent to Attention: Contracts Manager, ESRI, 380 New York Street, Redlands, CA 92373-8100, USA.

The information contained in this document is subject to change without notice.

DATA CREDITS

Highways and streets map—Maryland Department of Transportation State Highway Administration, Baltimore, Maryland

Transit map—Parsons Brinckerhoff Quade & Douglas, Inc., Los Angeles, California

Railways map—Parsons Brinckerhoff Quade & Douglas, Inc., Los Angeles, California

Oil and gas exploration map—TGS-NOPEC Geophysical Company, Houston, Texas

Pipelines map—M.J. Harden Associates, Inc., Kansas City, Missouri

Water resources map—Center for Research in Water Resources, University of Texas at Austin

Hatching map 1—New York State Department of Transportation, Albany, New York

Hatching map 2—TGS-NOPEC Geophysical Company, Houston, Texas

WRITER

Patrick Brennan

U.S. GOVERNMENT RESTRICTED/LIMITED RIGHTSAny software, documentation, and/or data delivered hereunder is subject to the terms of the License Agreement. In no event shall the U.S. Government acquire

greater than RESTRICTED/LIMITED RIGHTS. At a minimum, use, duplication, or disclosure by the U.S. Government is subject to restrictions as set forth in

FAR §52.227-14 Alternates I, II, and III (JUN 1987); FAR §52.227-19 (JUN 1987) and/or FAR §12.211/12.212 (Commercial Technical Data/Computer

Software); and DFARS §252.227-7015 (NOV 1995) (Technical Data) and/or DFARS §227.7202 (Computer Software), as applicable. Contractor/Manufacturer

is ESRI, 380 New York Street, Redlands, CA 92373-8100, USA.

ESRI, the ESRI globe logo, ArcGIS, ArcToolbox, ArcCatalog, ArcMap, ArcInfo, ArcSDE, GIS by ESRI, ArcView, ArcEditor, the ArcGIS logo, and www.esri.com

are trademarks, registered trademarks, or service marks of ESRI in the United States, the European Community, or certain other jurisdictions.

Other companies and products mentioned herein are trademarks or registered trademarks of their respective trademark owners.

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iii

Contents 1 Introduction 1Who uses linear referencing? 2Tips on learning about linear referencing 8

2 Quick-start tutorial 9Exercise 1: Organizing your data in ArcCatalog 10Exercise 2: Creating and calibrating route data 11Exercise 3: Displaying and querying routes 19Exercise 4: Displaying and querying route events 26Exercise 5: Editing routes 32

3 Linear referencing 39The need for linear referencing 40Routes and measures 43Route locations and route events 44Linear referencing and topology 45

4 Creating route data 47Route data 48Creating route feature classes 54Creating routes from existing lines 61Calibrating routes with points 67Migrating route data to a geodatabase 73

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iv LINEAR REFERENCING IN ARCGIS

125 Displaying and querying routes and events 77

The route identifier field 78Querying route data 79Hatching 83Displaying hatches 91Manipulating the text on hatches 99Hatch styles 101Route measure anomalies 104Dynamic segmentation 105Adding route events 107

6 Editing routes 109Adding the Route Editing toolbar 110Creating routes from existing lines 111Calibrating routes with points 117Route measures 119Remeasuring routes 121

7 Creating and editing event data 125Creating and editing event data 126Creating event tables in ArcCatalog 132Overlaying events 136Aggregating events 139Transforming event measures 141Locating points along routes 144Locating polygons along routes 146Editing event tables in ArcMap 148

Glossary 153

Index 161

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IN THIS CHAPTER

1

Introduction 1• Who uses linear referencing?

• Tips on learning about linearreferencing

Many organizations collect data about linear features, such as highways,city streets, railroads, rivers, and pipelines as well as water and sewernetworks. In most geographic information systems (GIS), these features aremodeled in two dimensions, using x,y coordinates. While these systemswork well for maintaining features with static characteristics, theseorganizations have realized that their linear features often havecharacteristics that are more dynamic in nature. To handle this, theseorganizations have developed one-dimensional linear referencing systems tomodel their data.

How these organizations store and utilize their linear referencing data variesnot only between the organizations themselves but also between thedepartments within the organizations. Because of this variance, there is aneed for flexible tools to create, display, query, analyze, and distributelinear referencing data.

ESRI® ArcGIS™ software contains a series of easy-to-use tools, wizards,and dialog boxes that assist you in meeting your linear referencing needs. Inthis book, you will learn how to create, calibrate, edit, display, and querythe data used in linear referencing.

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2 LINEAR REFERENCING IN ARCGIS

Most applications that use linear features can benefit from linear referencing. The following pages outline a few examples.

Highways and streets

Agencies that manage highways and streets use linear referencing in a variety of ways in their day-to-day operations. For example, linearreferencing is useful for assessing pavement conditions; maintaining, managing, and valuing assets (traffic signs and signals, guard rails,toll booths, loop detectors, etc.); organizing bridge management information; and reviewing and coordinating construction projects.Linear referencing also helps facilitate the creation of a common database that traffic planners, traffic engineers, and public worksanalysts can use for cross-disciplinary decision support.

Who uses linear referencing?

Pavement conditions along the highways that serve Baltimore, Maryland

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INTRODUCTION 3

Transit

Linear referencing is a key component in transit applications and facilitates such things as route planning and analysis; automaticvehicle location and tracking; bus stop and facility inventory; rail system facility management; track, power, communications, andsignal maintenance; accident reporting and analysis; demographic analysis and route restructuring; ridership analysis and reporting; andtransportation planning and modeling.

Corridor study showing the number of traffic accidents along an 18-mile stretch of the I-710 Freeway inLos Angeles County

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4 LINEAR REFERENCING IN ARCGIS

Railways

Railways use linear referencing to manage key information for rail operations, maintenance, asset management, and decision supportsystems. Linear referencing makes it possible, for example, to select a line and track and identify milepost locations for bridges andother obstructions that would prevent various types of freight movement along the route. Further, dynamic segmentation can be used todisplay track characteristics as well as to view digital images of bridges and obstructions.

Analyzing rail clearances along the Hudson rail line in downstate New York

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INTRODUCTION 5

Oil and gas exploration

The petroleum industry manages tremendous volumes of data used in geophysical exploration. Seismic surveys, or shotpoint data, areused to help understand the underlying geology in an area. The nature of seismic data is that it must be represented as both a linearobject—the seismic line—and a collection of point objects—the shotpoint. Both the seismic line and the individual shotpoints haveattributes, both must be maintained at the same time, and both are used in modeling applications. Linear referencing helps solve thisproblem.

Posting and labeling seismic lines and shotpoints in the Gulf of Mexico off of the Louisiana coast

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6 LINEAR REFERENCING IN ARCGIS

Pipelines

In the pipeline industry, linear referencing is often referred to as stationing. Stationing allows any point along a pipeline to be uniquelyidentified. As such, stationing is useful for collecting and storing information regarding pipeline facilities, both inline and physicalinspection histories, regulatory compliance information, risk assessment studies, work history events, and geographic information, suchas environmentally sensitive areas, political boundaries (state, county, etc.), right-of-way boundaries, and various types of crossings.

Pipeline coating material types in rural Kansas

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INTRODUCTION 7

Water resources

In hydrology applications, linear referencing is often called river addressing. River addressing allows objects, such as field monitoringstations, which collect information about water quality analysis, toxic release inventories, drinking water supplies, flow, and so on, to belocated along a river or stream system. Further, the measurement scheme used in river addressing allows for the measurement of flowdistance between any two points on a flow path.

Monitoring stations along the hydrology network of the Guadalupe River basin in southern Texas

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8 LINEAR REFERENCING IN ARCGIS

If you’re new to GIS, take some time to familiarize yourself withArcGIS. The books Using ArcCatalog, Using ArcMap, Editing inArcMap, and Building a Geodatabase contain tutorials to showyou how to create, edit, manage, and display GIS data.

Begin learning about linear referencing and dynamicsegmentation in Chapter 2, ‘Quick-start tutorial’, in this book. InChapter 2, you will learn how to create and calibrate route data,display and query route and event data, and edit route data.ArcGIS comes with the data used in this tutorial, so you canfollow along step by step at your computer. You can also read thetutorial without using your computer.

Finding answers to your questions

Like most people, your goal is to complete your tasks whileinvesting a minimum amount of time and effort in learning howto use software. You want intuitive, easy-to-use software thatgives you immediate results without having to read pages ofdocumentation. When you do have a question, however, you wantthe answer quickly so you can complete your task. That’s whatthis book is all about—getting you the answers you need whenyou need them.

This book describes how to accomplish linear referencing tasks.Although you can read this book from start to finish, you’ll likelyuse it more as a reference. When you want to know how to do aparticular task, such as identifying a route location, just look it upin the table of contents or index. What you’ll find is a concise,step-by-step description of how to complete the task. Somechapters also include detailed information that you can read ifyou want to learn more about the concepts behind the tasks. Youmay also refer to the glossary in this book if you come across anyunfamiliar GIS terms or need to refresh your memory.

Tips on learning about linear referencing

Getting help on your computer

In addition to this book, the ArcGIS Desktop Help system is avaluable resource for learning the software. To learn how to useHelp, see Using ArcMap.

Contacting ESRI

If you need to contact ESRI for technical support, see the productregistration and support card you received with ArcGIS or referto ‘Contacting Technical Support’ in the ‘Getting more help’section of the ArcGIS Desktop Help system. You can also visitESRI on the Web at www.esri.com and support.esri.com for moreinformation on linear referencing and ArcGIS.

ESRI education solutions

ESRI provides educational opportunities related to geographicinformation science, GIS applications, and technology. You canchoose among instructor-led courses, Web-based courses, andself-study workbooks to find educational solutions that fit yourlearning style. For more information, go to www.esri.com/education.

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IN THIS CHAPTER

9

Quick-start tutorial 2• Exercise 1: Organizing your data

in ArcCatalog

• Exercise 2: Creating andcalibrating route data

• Exercise 3: Displaying andquerying routes

• Exercise 4: Displaying andquerying route events

• Exercise 5: Editing routes

ArcGIS has the tools you need for linear referencing applications. The easiestway to start learning about linear referencing is to complete the exercises in thistutorial. Before you start, however, it is assumed you know the fundamentals ofArcToolbox™, ArcCatalog™, and ArcMap™ software. For more information, seeUsing ArcToolbox, Using ArcCatalog, Using ArcMap, and Editing in ArcMap.

For this tutorial, imagine that you work in the GIS department of a highwayauthority responsible for the maintenance and safety of your region’s highways. Inthe exercises to follow, you will perform some of the linear referencing taskstypical to such a person. Specifically, you will use ArcToolbox to create andrecalibrate route data. Next, you will learn how to display and query your newlycreated route data in ArcMap. After that, you will discover how easy it is todisplay and query your route event data in ArcMap. Lastly, you will learn how toedit your route data in ArcMap.

To complete many of the exercises in this tutorial, you will need to have anArcInfo™ license. Feel free, however, to read through the exercises to familiarizeyourself with the linear referencing functionality in ArcGIS.

Work on this tutorial at your own pace. The exercises build on one another, so it isassumed that you will complete them in order. This tutorial includes five exercises,each of which takes five to 30 minutes to complete.

The study area for this tutorial is Pitt County, North Carolina. The data wascompiled from various sources and has been modified to suit the needs of theexercises. The reliability and suitability of the information, therefore, cannot beguaranteed.

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10 LINEAR REFERENCING IN ARCGIS

Exercise 1: Organizing your data in ArcCatalog

The exercises in this chapter use the tutorial data distributedwith ArcGIS. The default install location of the data isC:\arcgis\ArcTutor\LinearReferencing. Some of thefollowing exercises require that you change the data. Youwill, therefore, need to have write access to the data. If youdo not want to change the data at the default location oryou do not have write access, you will need to copy theLinearReferencing folder to a new location before you startthe exercises.

Connecting to the data

In ArcCatalog, folder connections let you access directorieson local disks or shared folders on the network. Further,database connections allow you to access the contents of adatabase.

1. Start ArcCatalog by either double-clicking a shortcutinstalled on your desktop or using the Programs list inyour Start menu.

2. Click the Connect To Folder button on the Standardtoolbar.

3. Navigate to the LinearReferencing folder on the localdrive where you installed the tutorial data.

4. Click OK.

The new folder connection is now listed in the Catalog tree.You will now be able to access all of the data needed forthe remaining exercises in this tutorial via the newconnection.

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QUICK-START TUTORIAL 11

Exercise 2: Creating and calibrating route data

The first thing you will need for any linear referencingproject is accurate route data. In this exercise, you will firstcreate a route feature class by merging input line featuresthat share a common route identifier. This is done with theCreate Routes Wizard, which is in ArcToolbox.

Next, you will recalibrate the newly created route featureclass using a point feature class that stores route andmeasure information as attributes. This is done with theCalibrate Routes Wizard, which is also in ArcToolbox.

Creating route data

The Create Routes Wizard is used to specify the input linefeature class, the route identifier field, the method used toset the route measures, and the output feature class. Notethat the input feature classes can be any supported format.This includes coverage, shapefile, personal and enterprisegeodatabase, and computer-aided design (CAD) data.

1. Start ArcToolbox by either double-clicking a shortcutinstalled on your desktop or using the Programs list inyour Start menu.

2. Double-click the Create Routes Wizard in ArcToolbox inthe Linear Referencing toolset of Data ManagementTools.

There are several ways to set the input feature class. Youcan drag a line feature class from the ArcCatalog tree anddrop it onto the text box, click the Browse button to openthe ArcCatalog minibrowser and navigate to the featureclass, or simply type the full pathname to the feature classin the text box.

The tutorial instructions will simply ask you to type namesand paths into the appropriate text boxes. Feel free,however, to use any of the available techniques.

3. Type “C:\arcgis\ArcTutor\LinearReferencing\PITT.mdb\PITT\base_roads” for the Input FeatureClass.

4. Click the Route Identifier Field dropdown arrow andclick ROUTE1. The values in the route identifier fielduniquely identify each route.

5. Click Next.

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12 LINEAR REFERENCING IN ARCGIS

This panel asks you to specify how the route measures willbe obtained. There are three choices:

• The geometric lengths of the input features are used toaccumulate the measures.

• A value stored in a measure field is used to accumulatethe measures.

• The values stored in from- and to-measure fields areused to set the measures.

You will use the third method.

6. Click Use two fields from the input feature class.

7. Click the From-Measure field dropdown arrow and clickBEGMP1.

8. Click the To-Measure field dropdown arrow and clickENDMP1.

9. Click Next.

The output routes can be written to a shapefile or ageodatabase feature class. You will be writing to a newfeature class in the same feature dataset as the inputfeature class.

10. Click Feature class in a geodatabase.

11. Click Next.

If your input features have a defined projection, the CreateRoutes Wizard will preserve this projection. You can chooseto change the projection information for the output, in whichcase the features will automatically be projected. Note thatyou cannot change the projection if you are writing to anexisting feature dataset.

Whenever writing routes to a geodatabase, you shouldalways set the m domain. A default m domain will becalculated for you, but this might not accurately reflect yourneeds.

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QUICK-START TUTORIAL 13

12. Type “C:\arcgis\ArcTutor\LinearReferencing\PITT.mdb” for the Output Geodatabase.

13. Click the dataset dropdown arrow and click the PITTdataset.

14. Type “routes” for the name of the new feature class.

15. Click Change Settings.

17. Click the M Domain tab.

18. Type “-1000” for the Min and “10000” for the Precision.These settings will ensure that your route measures willbe accurate to four decimal places.

19. Click OK.

20. Click OK on the Output Settings dialog box.

At this point, you will have returned to the Enter theoutput feature class panel.

21. Click Next on the Create Routes Wizard.

16. Click Change.

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14 LINEAR REFERENCING IN ARCGIS

��

Not all features from the input feature class have route andmeasure information. These features represent roads thatare not currently maintained by the highway authority anddo not need to be included in the output route feature class.You will exclude these features from the route creationprocess by specifying a query.

22. Click Use only those features that satisfy a query.

23. Click the Click to define a query button.

24. Type “[ROUTE1] < > 0” in the text box.

25. Click OK.

26. Click Next on the Create Routes Wizard.

27. Review your settings and click Finish.

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QUICK-START TUTORIAL 15

Calibrating route data

Imagine that at some point in the future, the highwayauthority’s road maintenance crew acquired a distancemeasuring instrument (DMI) so that they could accuratelyrecord mileage information along the highways. For asample set of highways, the crew went out and capturedmileage information approximately every 1/10 of a mile.The results of this effort were stored as points in ashapefile, where the route and mileage information wasstored as attributes.

In the next section of this tutorial, you will use the CalibrateRoutes Wizard to adjust the measures of the routes you justcreated to match those of the points in the shapefile. Theresult will be written to a new feature class.

The Calibrate Routes Wizard is used to specify the inputroute feature class, the route identifier field, the input pointfeature class, the measure field, the methods used to set theroute measures, and the output feature class. Note that theinput route feature classes can be any supported format.This includes coverage, shapefile, personal and enterprisegeodatabase, and CAD data.

Note that in addition to being able to adjust the measures ofexisting routes, the Calibrate Routes Wizard can also beused to create new routes by merging unmeasured inputline features using a common route identifier and setting themeasure information using the point attributes. To mimic theacquisition of more accurate data over time, however, theprocess was split into two separate tasks for this exercise.

1. Double-click the Calibrate Routes Wizard in ArcToolboxin the Linear Referencing toolset of Data ManagementTools.

2. Type “C:\arcgis\ArcTutor\LinearReferencing\PITT.mdb\PITT\routes” for the Input Feature Class.

3. The values in the route identifier field uniquely identifyeach route. Click the Route Identifier Field dropdownarrow and click ROUTE1.

4. Click Next.

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16 LINEAR REFERENCING IN ARCGIS

5. Type “C:\arcgis\ArcTutor\LinearReferencing\Calibration_Points.shp” for the Point Feature Class.

6. Click the Point Identifier Field dropdown arrow and clickROUTE1.

7. Click the Measure dropdown arrow and clickMEASURE.

A tolerance can be specified to limit how far a calibrationpoint can be from its route. Points outside the tolerance willnot be used by the calibration process. The tolerance isexpressed in the same units as the route feature class’scoordinate system.

8. Type “5” for the tolerance. This is more than enough forthe data that is being used here.

9. Click Next.

If your point features have a projection that differs from theroute features, the Calibrate Routes Wizard will project thepoints to match the routes before the calibration processstarts.

Either whole or partial routes can be calibrated. You canchoose to interpolate between the input points, extrapolatebefore the input points, extrapolate after the input points, oruse any combination of these three methods.

Note that the Extrapolate before calibration points,Interpolate between calibration points, and Extrapolate aftercalibration points check boxes are checked by default.

10. Click Next.

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QUICK-START TUTORIAL 17

The output routes can be written to a shapefile or ageodatabase feature class. You will be writing a newfeature class in the same feature dataset as the inputroutes.

11. Click Feature class in a geodatabase.

12. Click Next.

13. Type “C:\arcgis\ArcTutor\LinearReferencing\PITT.mdb” for the Output Geodatabase.

14. Click the dataset dropdown arrow and click the PITTdataset.

15. Type “routes_new” for the name of the new featureclass.

16. Click Change Settings.

17. Click Change.

Note that whenever you create a feature class in ageodatabase, you should always check to make surethat the spatial domains are correct. In this tutorial, youwill only check the m domain.

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18 LINEAR REFERENCING IN ARCGIS

18. Click the M Domain tab.

19. Type “-1000” for the Min and “10000” for the Precision.These settings will ensure that your route measures willbe accurate to four decimal places.

20. Click OK.

21. Click OK.

At this point, you will have returned to the Enter theoutput feature class panel.

22. Click Next.

23. Click Next.

24. Review your settings and click Finish.

In this exercise, you learned how to create a route featureclass by merging input line features that shared a commonidentifier and how to adjust the route measures usingmeasure information stored in a point shapefile. For moreinformation on creating and calibrating route data, seeChapter 4, ‘Creating route data’.

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QUICK-START TUTORIAL 19

Exercise 3: Displaying and querying routes

In this exercise, you will add the route data you created inExercise 2 to an existing map document and symbolize it.You will then

• Set the route identifier field.

• Add the Identify Route Locations tool to a toolbar.

• Identify route locations.

• Find route locations.

• Display route measure anomalies.

Opening an existing map document

Before you can complete this exercise, you must startArcMap.

1. Double-click a shortcut installed on your desktop or usethe Programs list in your Start menu to start ArcMap.

2. Click Open from the ArcMap File menu.

3. Click the Look in dropdown arrow in the Open dialogbox and navigate to the folder where you installed thedata for this tutorial.

4. Double-click Ex3.mxd. ArcMap opens the map.

This map contains the following layers in a data framecalled Pitt County:

calibration_points The points used in Exercise 2 to recalibrate the route measures

base_roads All of the roads in Pitt County

city boundaries The boundaries of the cities in PittCounty

county boundary Pitt County boundary

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20 LINEAR REFERENCING IN ARCGIS

The map currently displays the city boundaries and countyboundary layers. Their check boxes are checked in thetable of contents. The calibration_points layer is checked,but scale suppression has been set. It will only be visiblewhen you zoom in to a scale beyond 1:25,000.

5. Click the check box for the base_roads layer in the tableof contents.

You will now see all of the roads in Pitt County. Thisincludes roads not maintained by the highway authority. Theroads maintained by the highway authority were written tothe routes feature class.

Adding route data to your map

1. Click the Add Data button on the ArcMap Standardtoolbar.

2. Click the Look in dropdown arrow and navigate towhere you installed tutorial data. Double-click Pitt.mdband double-click the Pitt feature dataset.

3. With the Ctrl key pressed down, select both the routesand routes_new feature classes.

4. Click Add. You will see two new layers in the table ofcontents.

Changing the display symbol

The colors and symbols ArcMap chose to display for theroutes layer might make it difficult to see where the routefeatures are located. It is easy to change the colors andsymbols used to display features in ArcMap.

1. Click the line symbol in the table of contents for theroutes layer to display the Symbol Selector dialog box.

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QUICK-START TUTORIAL 21

2. Scroll down until you find a symbol you like and click it.

3. Click OK. Your routes layer will be displayed with thesymbol you chose.

4. Repeat steps 1 through 3 for the routes_new layer.

You can also open the Symbol Selector dialog box by right-clicking the layer in the table of contents, clickingProperties, and clicking the Symbology tab. To simplychange the color of a symbol, right-click the symbol in thetable of contents to display the color palette. For moreinformation on changing display symbols, see UsingArcMap.

Setting the Route Identifier field

ArcMap knows whenever route data has been added to amap and exposes some additional layer properties. One ofthese properties is the Route Identifier field. This fielduniquely identifies each route.

Setting the Route Identifier field is not required. Doing so,however, reduces the number of steps required to use manyof the ArcMap Linear Referencing dialog boxes, wizards,and tools.

1. Right-click the routes layer in the table of contents andclick Properties.

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22 LINEAR REFERENCING IN ARCGIS

2. Click the Routes tab.

3. Click the Route Identifier dropdown arrow and clickROUTE1.

4. Click OK.

� �

1. Click Customize from the ArcMap Tools menu.

2. Click the Commands tab.

3. Click Linear Referencing in the Categories list.

4. Drag the Identify Route Locations tool to the toolbar ofyour choice (e.g., the Tools toolbar).

5. Click Close.

5. Repeat steps 1 through 4 for the routes_new layer.

Adding the Identify Route Locations tool

ArcMap gives you the ability to point to a route in a mapand find the route identifier and measure value at thatlocation. In this part of the exercise, you will use theIdentify Route Locations tool to inspect the measures onthe routes you created in Exercise 2.

The Identify Route Locations tool does not appear on anytoolbar by default. You will have to add it to one.

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QUICK-START TUTORIAL 23

Identifying route locations

In ArcMap, a bookmark is a saved map location. Abookmark containing some of the calibration points used inExercise 2 to recalibrate the routes has been created foryou.

1. Point to Bookmarks from the ArcMap View menu andclick Calibration Points.

When ArcMap moves to the saved location, the calibrationpoints appear with labels that represent the measure valuesfor each point. The reason they appear when the bookmarkhas been used is because scale suppression was set on thelayer. For more information on scale suppression, see UsingArcMap.

2. Click the Identify Route Locations button.

3. Move the mouse pointer over one of the calibrationpoints and click. Route locations from both the routesand routes_new layers will be identified.

4. Click the route node for each of the route layers.

The numeric value listed for each of these nodescorresponds to the value stored in the Route Identifierfield, which you set in a previous section of thisexercise. Note that the measure value for the two routesdiffers. Note further that the measure value for theroutes_new layer corresponds closely to the measurevalue of the calibration point you clicked (the closer youare to a calibration point, the closer the measure will be).

5. Right-click the route node for one of the layers andexplore the context choices available to you.

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24 LINEAR REFERENCING IN ARCGIS

6. Uncheck the check box for the calibration_points layerin the table of contents to make it not visible. It will notbe used any further in this exercise.

7. Close the Identify Route Location Results window.

Finding route locations

In many linear referencing applications, you will discoverthat you will often need to find a location along a route. Forexample, you may need to find where an accident occurredalong a highway. On a paper map, it is hard to find a routelocation. This is because route measures are typically notshown. In ArcMap, finding a route location is made easy.

1. Click the Find button on the ArcMap Tools toolbar.

2. Click the Route Locations tab.

3. Click the Route Reference dropdown arrow and clickroutes_new.

Notice that the field listed in the Route Identifier dropdownarrow corresponds to the Route Identifier field you setpreviously in this exercise.

4. Type “30000121” in the Route text box.

5. Type “5” in the Location text box.

6. Click Find.

7. Right-click the route location that was found and explorethe context choices available to you.

8. Close the Find dialog box.

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QUICK-START TUTORIAL 25

��

Displaying route measure anomalies

In most linear referencing applications, route measurevalues are expected to follow a set of rules. For example,you might expect that route measures always increase overthe course of a route. ArcMap has the ability to show youwhere route measures do not adhere to the behavior youexpect. These are known as route measure anomalies.

1. Click the Full Extent button on the ArcMap Toolstoolbar.

2. Right-click the routes layer in the table of contents andclick Properties.

3. Click the Routes tab.

4. Check Show where measures do not increase.

5. Click the Line Symbol button and select a line symbolyou like. Do the same for the marker symbol.

6. Click OK.

Remember that the routes feature class was created fromthe base_roads feature class in Exercise 2. There are afew digitizing errors and a few attribute errors that causedthe measure anomalies to exist in the routes feature class.Route measure anomalies can be fixed with ArcMap routeediting tools. For more information on route editing tools,see Chapter 6, ‘Editing routes’.

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26 LINEAR REFERENCING IN ARCGIS

Exercise 4: Displaying and querying route events

In this exercise, you will create a new event table thatrepresents where injury accidents occurred along sectionsof poor-quality pavement. To do this, you will first use theAdd Route Events dialog box to display the accidentlocation and pavement quality event data on your map. Youwill then use the Select By Attributes dialog box to selectthe injury accidents and poor-quality pavement locations.Finally, you will use the Route Events GeoProcessingWizard to create a new event table whose recordsrepresent where injury accidents occurred along poor-quality pavement.

Opening an existing map document

Before you can complete this exercise, you must startArcMap.

1. Double-click a shortcut installed on your desktop or usethe Programs list in your Start menu to start ArcMap.

2. Click Open from the ArcMap File menu.

3. Click the Look in dropdown arrow in the Open dialogbox and navigate to the folder where you installed thedata for this tutorial.

4. Double-click Ex4.mxd. ArcMap opens the map.

This map contains the following layers in a data framecalled Pitt County:

routes_hwy Shapefile copy of routes_newfeature class you created inExercise 2

county boundary Pitt County boundary

accident Point event table storing accidentinformation

pavement Line event table storing pavementinformation

base_roads All of the roads in Pitt County

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QUICK-START TUTORIAL 27

Displaying point events on your map

The accident table is a point event table. Point events occurat a precise point location along a route. In this section ofthe exercise, you will display the accident event data as alayer.

1. Click Add Route Events from the ArcMap Tools menu.

2. Click the Route Reference dropdown arrow and clickroutes_hwy.

3. Click the Route Identifier dropdown arrow and clickROUTE1.

4. Click the Event Table dropdown arrow and clickaccident.

5. Click the Route Identifier dropdown arrow and clickROUTE1.

6. Click the Measure dropdown arrow and clickMEASURE.

7. Click OK.

A new layer—accident Events—has been added to yourmap.

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28 LINEAR REFERENCING IN ARCGIS

Displaying line events on your map

The pavement table is a line event table. Line events differfrom point events in that they have two measure fields thatdefine a portion of a route. The procedure for adding lineevents to your map is almost the same as adding pointevents.

1. Click Add Route Events from the ArcMap Tools menu.

2. Click the Route Reference dropdown arrow and clickroutes_hwy.

3. Click the Route Identifier dropdown arrow and clickROUTE1.

4. Click the Event Table dropdown arrow and clickpavement.

5. Click the Route Identifier dropdown arrow and clickROUTE1.

6. Click Line Events.

7. Click the From-Measure dropdown arrow and clickBEGIN_MP.

8. Click the To-Measure dropdown arrow and clickEND_MP.

9. Click OK.

A new layer—pavement Events—has been added to yourmap.

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QUICK-START TUTORIAL 29

Querying events

Layers based on an event table can be queried in manyways. They can be identified by clicking them, they can beselected by dragging a box or clicking them on the map,they can be selected by clicking them in an attribute table,and they can be selected using a Structured QueryLanguage (SQL) expression. You will use the Select ByAttributes dialog box to input SQL expressions to select theevent records needed for this exercise. Specifically, you willselect injury accidents and poor quality pavement.

1. Click Select By Attributes from the ArcMap Selectionmenu.

2. Click the Layer dropdown arrow and click accidentEvents.

3. Type the following in the text box:“NUM_INJURY” > 0

4. Click Apply.

5. Click the Layer dropdown arrow and click pavementEvents.

6. Type the following in the text box: “RATING” < 50

7. Click Apply.

8. Click Close.

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30 LINEAR REFERENCING IN ARCGIS

There are many events selected on your map. In the nextsection of this exercise, you will use the Route EventsGeoProcessing Wizard to intersect the two event layers.The result will be a table that contains the injury accidentsthat happened on poor-quality pavement. All attributes fromboth inputs are maintained.

Intersecting event layers

1. Click Route Events GeoProcessing Wizard from theArcMap Tools menu.

2. Intersect two route event layers is the default. ClickNext.

3. Click the input route event layer dropdown arrow andclick accident Events.

4. Click the overlay route event layer dropdown arrow andclick pavement Events.

5. Click Next.

6. Type “C:\arcgis\ArcTutor\LinearReferencing\AccPav.dbf” for the output route event table.

7. Click Finish.

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QUICK-START TUTORIAL 31

A new layer—AccPav Events—will be added to your map.It will be hard to see, however, because the accident andpavement event layers are still visible.

8. Turn off the accident and pavement layers by clickingtheir check boxes in the table of contents.

You will now see only the injury events that occurred alongpoor quality pavement. Each of these new events has all ofthe attributes from both the accident and pavement tables.

For more information on the display and query of events orthe spatial analysis of events, see Chapter 5, ‘Displayingand querying routes and events’, and Chapter 7, ‘Creatingand editing event data’.

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32 LINEAR REFERENCING IN ARCGIS

Exercise 5: Editing routes

There are a number of tools in ArcMap that make theinteractive creation and editing of route measures easy. Inthis exercise, you will create a new route from a selectedset of linear features and set its identifier. You will thenconvert the measures of this newly created route from feetto miles. Lastly, you will recalibrate the route using knownmeasure values at specific locations on your map.

Opening an existing map document

Before you can complete this exercise, you must startArcMap.

1. Double-click a shortcut installed on your desktop or usethe Programs list in your Start menu to start ArcMap.

2. Click Open from the ArcMap File menu.

3. Click the Look in dropdown arrow in the Open dialogbox and navigate to the folder where you installed thedata for this tutorial.

4. Double-click Ex5.mxd. ArcMap opens the map.

Adding route data to your map

You will use one of the route feature classes you created inExercise 2 to complete this exercise.

1. Click the Add Data button on the ArcMap Standardtoolbar.

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QUICK-START TUTORIAL 33

2. Click the Look in dropdown arrow, navigate to whereyou installed tutorial data, double-click Pitt.mdb, anddouble-click the Pitt feature dataset.

3. Double-click the routes_new feature class. You will seea new layer in the table of contents.

Adding the toolbars, editing, and setting the targetfeature class

The toolbars necessary to complete this exercise might notbe visible.

1. Click the Editor Toolbar button on the ArcMap Standardtoolbar to add the Editor toolbar to ArcMap.

2. Click the Editor menu, point to More Editing Tools, andclick Route Editing.

3. Click the Editor menu and click Start Editing.

4. Click the Target dropdown arrow and click routes_new.

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34 LINEAR REFERENCING IN ARCGIS

Making a route from selected features

The highway authority has been informed that it will now beresponsible for maintaining a road that it previously had notbeen maintaining. It is necessary, therefore, to select theappropriate features from the base_roads feature class andmake a route in the routes_new feature class out of them.

The Make Route command creates a new route in thetarget feature class by merging a selected set of linefeatures and setting the measure values. The selected linefeatures do not need to be from the target feature class.

1. Click Select By Attributes from the ArcMap Selectionmenu.

2. Click the Layer dropdown arrow and click base_roads.

3. Type the following in the text box:[FENAME] = ‘Cornerstone Row’

4. Click Apply.

5. Click Close.

Nine features from the base_roads feature class are nowselected.

6. Right-click the base_roads layer in the table of contents,point to Selection, and click Zoom To Selected Features.

� �

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QUICK-START TUTORIAL 35

7. Click the Make Route button on the Route Editingtoolbar.

8. Click the Start Point button.

9. Click the mouse pointer on the map near the upper-rightcorner of the selected set of features. This is where theoutput route’s measures will begin.

10. Click Make Route.

The new route will flash when it is being created. Duringthe route creation process, the selected lines will beunselected, and the new route will be selected. This is soyou can set the new route’s attributes.

Setting the Route Identifier

Because the newly created route is selected, you can nowset the route identifier. The route identifier uniquelyidentifies each route.

1. Click the Attributes button on the Editor toolbar.

2. Click the ROUTE1 value and type “40001777”.

3. Press Enter.

4. Close the Attributes dialog box.

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36 LINEAR REFERENCING IN ARCGIS

Converting route measure units

When you created the new route, you accepted the defaultmethod for setting the route measures. This methodaccumulates the geometric length of the input line featuresand uses the length as the measure. Because the coordinatesystem of the feature class is State Plane Feet, this meansthat the measures on the new route are feet. However, themeasures on all other routes in the feature class are miles.

1. The newly created route should still be selected. If it isnot, select it.

2. Click the Task dropdown arrow and click ModifyFeature.

The selected feature will now be loaded into the editsketch.

3. Click the Sketch Properties button. Note the measurevalues.

4. Close the Edit Sketch Properties dialog box.

5. Right-click anywhere over the edit sketch, point to RouteMeasure Editing, and click Apply Factor.

6. Type “0.00018939” in the Factor text box and pressEnter. This converts feet to miles.

At this point, you have only made changes to the editsketch, not the route feature.

7. Press F2 to finish the edit sketch. Alternately, right-clickanywhere over the edit sketch and click Finish Sketch.

Your route measures are now in miles. You can verify thisby double-clicking the selected route to bring it into the editsketch, right-clicking anywhere over the sketch, andclicking Properties. Note that this is an alternate way toperform Steps 2 and 3.�

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QUICK-START TUTORIAL 37

Recalibrating a route

So far in this exercise, you have created a route andtransformed its measures from feet to miles. Imagine thatat some point the maintenance crew went out into the fieldand recorded the actual mileage for this new route. Themileage was captured every time the new route intersectedwith another route from the same feature class. In thissection of the exercise, you will recalibrate the newlycreated route based on this mileage information.

1. The newly created route should still be selected. If it isnot, select it.

2. Click the Editor menu and click Snapping.

3. Check the End check box next to the routes_new layer.

4. Close the Snapping Environment dialog box. It will notbe used again in this exercise.

With the snapping environment set, you will be able tocreate calibration points that are snapped to the end vertexof the features in the routes_new layer, thereby ensuringaccuracy of the route measures at the calibration points.Setting the snap environment, however, is not necessary forthe Calibrate Route command to work.

5. Click the Task dropdown arrow and click CalibrateRoute Feature.

6. Click the Calibrate Route button on the Route Editingtoolbar.

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38 LINEAR REFERENCING IN ARCGIS

1

2

3

4

56

7

89

The Calibrate Route dialog box is now on the screen, but itis empty. Your next task is to digitize the calibration points.

7. With the Calibrate Route dialog box open, click theSketch tool on the Editor toolbar.

8. Click along the route at nine different places to createthe calibration points. The locations of the calibrationpoints are indicated in the graphic below.

9. Type the New M value (see values in graphic below) foreach calibration point.

10. Click Calibrate Route.

Saving your edits

Once you have completed the steps in this exercise, youcan choose to save or discard your edits by stopping the editsession.

1. Click the Editor menu and click Stop Editing.

2. Click Yes to save your edits or No to discard your edits.

In this exercise, you first learned how to create a routefrom a selected set of line features. Next, you convertedthe route measures from feet to miles. Lastly, you learnedhow to recalibrate a route using calibration points youdigitized on the map.

For more details about the route editing tools outlined hereor for information on tools not discussed in this chapter, seeChapter 6, ‘Editing routes’.

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IN THIS CHAPTER

39

Linear referencing 3• The need for linear referencing

• Routes and measures

• Route locations and route events

• Linear referencing and topology

Highways, city streets, railroads, rivers, pipelines, and water and sewernetworks are all examples of linear features. Linear features typically haveonly one set of attributes. Linear referencing, however, provides you with anintuitive way to associate multiple sets of attributes to portions of linearfeatures. With linear referencing, your ability to understand, maintain, andanalyze linear features is greatly improved.

This chapter outlines the way linear features are modeled in ArcGIS. It thenintroduces you to what linear referencing is, explains why it is needed, andoutlines the concepts necessary to develop linear referencing applications.Once you understand the concepts introduced in this chapter, you can refer tolater chapters in this book to use the wide range of linear referencingfunctionality in ArcGIS.

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Geographic data is modeled in a number of ways: as a collectionof features in vector format, as a grid of cells with spectral orattribute data in raster format, or as a set of triangulated pointsmodeling a surface in triangulated irregular network (TIN)format.

Data that has a discrete location with a defined shape andboundary is modeled using the vector format. In this format, datais represented by features. Features are stored in feature classes.Every feature has a geometry associated with it. This geometry isstored in a special field that is typically called shape. A featurecan have one of these types of geometries: point, multipoint,polyline, or polygon. Each geometry is composed of two-dimensional (x,y) or three-dimensional (x,y,z) geographiccoordinates.

The need for linear referencing

The vector format works well for modeling features with staticcharacteristics, such as parcel boundaries, water bodies, and soilcharacteristics. Some applications, however, require the ability tomodel the relative location along various linear features, such ashighways, city streets, railroads, rivers, pipelines, and water andsewer networks.

Because of this need, one-dimensional measuring systems, suchas river mile and route milepost, have been devised. Thesesystems simplify the recording of data by using a relative positionalong an already existing linear feature. That is, location is givenin terms of a known linear feature and a position, or measure,along it. For example, route I-10, mile 23.2, uniquely identifies aposition in geographic space without having to express it in x,yterms.

When data is linearly referenced, multiple sets of attributes canbe associated with any portion of an existing linear feature,independent of its beginning and end. These attributes can bedisplayed, queried, edited, and analyzed without affecting theunderlying linear feature’s geometry.

The need to visually represent features on a map whosecoordinates are not geographic but are recorded as a relativedistance along another linear feature led to the development ofdynamic segmentation. Dynamic segmentation is the process ofdisplaying linearly referenced features on a map. For moreinformation on dynamic segmentation, see Chapter 5, ‘Displayingand querying routes and events’.

In the vector format, geographic data is stored as a feature that has ageometry type of point, multipoint, polyline, or polygon.

Y

X

(1,2)

(3,3)

(5,1)

(7,5)

(8,2)

(9,5) (12,5)

(12,2)

(11,3)

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LINEAR REFERENCING 41

Storing features as relative locations

Locating a spatial feature along another linear feature wouldtypically be done using a planar (two-dimensional) referencingsystem of x,y coordinates.

This works well in some applications. In others, however,locations along linear features are referred to in terms of theirdistance from a known point. For example, it makes much moresense to record the location of an accident as occurring at“12 miles from the beginning of the interstate” rather than at“1659060.25, 1525238.97”.

To determine a location along a linear feature, a system ofmeasurement is required. When a measurement system is storedwith a linear feature, any location along that linear feature can beexpressed in terms of the measure values.

In addition to making data more intuitive, storing data as arelative location along a linear feature has the added benefit ofensuring that spatial phenomena you know to be along a linearfeature is mapped as such. For example, in the absence of anaccurate basemap, locating accidents using x,y coordinates mayend up displaying accidents that do not fall along the roadnetwork. This cannot happen if the accidents are stored asmeasurements along the linear features of the road network.

Segmented data

The vector model of data storage dictates that you must split alinear feature wherever its attribute values change. Certain linearfeatures, however, have attributes that change frequently. Thepavement condition of a road, for example, changes as pavementdeteriorates and is subsequently repaired. To accurately reflectthe changes in pavement condition, you will have to split somefeatures and merge others.

Segmenting the linear features becomes more problematic whenyou need to store other attributes, such as traffic volumes, laneinformation, surface material, speed limits, and accidentlocations. Every time these attributes change, the road will needto be further subdivided. With all the required segmenting, it isevident that the linear features will be so subdivided that the datawill be difficult, if not impossible, to maintain.

To attach attributes describing pavement quality, it is necessary to split alinear feature at several locations to reflect changes in data. Over time,pavement quality changes, requiring features to be split or merged.

02/2002 Fair Good Poor Good

10 20 30 40

08/2001 Fair Good Poor Good

Locating accidents using x,y coordinatesX

Y

(x,y)(x,y)

(x,y)

Locating accidents using measure values

1222

0 10

20 30

3

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42 LINEAR REFERENCING IN ARCGIS

ArcGIS uses route event tables to store linearly referencedattributes. Event rows are composed of a route identifier, measurevalues indicating a location, and one or more attributes describingthe location. For more information on route event tables, see‘Route locations and route events’ in this chapter.

Because events simply reference measure locations along linearfeatures, they are edited and maintained independently of thelinear features. For more information on maintaining event data,see Chapter 7, ‘Creating and editing event data’.

Speed 45 35 45 55

Asphalt Concrete AsphaltMaterial

2 4Lanes

10 20 30 40

Accidents

Quality Fair Good Poor Good

Storing multiple sets of attributes for one feature is made possible usinglinear referencing.

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LINEAR REFERENCING 43

Routes and measures

When linearly referenced features in ArcGIS are referred to, theterms routes and route events are used. A route is any linearfeature, such as a city street, highway, river, or pipe, that has aunique identifier and a measurement system. This measurementsystem defines discrete locations along the linear feature. Formore information on route events, see ‘Route locations and routeevents’ in this chapter.

A collection of routes with a common system of measurement canbe stored in a single feature class—for example, a set of allhighway routes in a county. In a geodatabase, many featureclasses containing routes can be stored in a single feature dataset.For example, a state’s department of transportation (DOT) mightmaintain a feature dataset with feature classes for milepost routes,reference marker routes, and so on.

Linear features and, therefore, routes are stored in a feature classwhose geometry type is a polyline. A polyline is an orderedcollection of paths that can be connected or disjointed. Polylinesare used to represent such things as roads, rivers, and contours.

A feature dataset can have multiple feature classes that store routes.

Polylines can have a measurement system stored with theirgeometry. Instead of being a collection of segments with x,ycoordinates, a measured polyline’s segments have x,y and m(measure) or x,y,z and m values. When a measure value isunknown, it is listed as NaN (not a number).

It is important to note that although many applications usemeasures to represent increasing distances along a linear feature,measure values can arbitrarily increase, remain constant, ordecrease.

Measure values are independent of the coordinate system of afeature class. That is, the measure values are not required to be inthe same units as the feature class’s x,y coordinates. For example,features stored in a feature class whose coordinate system isUniversal Transverse Mercator (UTM) meters might havemeasure values stored in feet or miles.

Polylines can have a measurement system stored with their geometry.Measures can be unknown (NaN).

010

20

300

NaN

NaN

30

A polyline is an ordered collection of paths that can be connected ordisjointed.

Polyline with one path Polyline with multiple,connected paths

Polyline with multiple,disjointed paths

A route is a linear feature with a unique identifier and a measurementsystem.

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44 LINEAR REFERENCING IN ARCGIS

Route locations and route events

A route location describes a discrete location along a route(point) or a portion of a route (line). A point route location usesonly a single measure value to describe a discrete location alonga route. An example of a point route location is “mile 3.2 on theI-91.” A line route location uses both a from- and a to-measurevalue to describe a portion of a route. “Mile 2 to mile 4 onthe I-91” is an example of a linear route location.

When route locations—and their associated attributes—arestored in a table, they are known as route events or simply events.Events are organized into tables based on a common theme. Forexample, five event tables containing information on speedlimits, year of resurfacing, present condition, signs, and accidentscan reference highway routes.

Route event tables

Because there are two types of route locations, there are twotypes of route event tables: point and line.

A route event table, at a minimum, consists of two fields: a routeidentifier and a measure location. The route identifier field is anumeric or character value used to identify the route to which anevent belongs. A measure location is either one or two fields thatdescribe the positions along the route at which the event occurs.These values can be defined as any numeric item.

An event table can be any type of table that ArcGIS supports.This includes INFO™, dBASE®, geodatabase tables, delimitedtext files, and database management system tables accessed viaan OLE DB connection.

Point events

Point events occur at a precise point location along a route.Accident locations along highways, signals along rail lines, busstops along bus routes, and pumping stations along pipe lines areall examples of point events. Point events use a single measurevalue to describe their location.

Line events

Line events describe portions of routes. Pavement quality, salmonspawning grounds, bus fares, pipe widths, and traffic volumes areall examples of line events. Line events use two measure valuesto describe their location.

Events are located along a route using their route location information.Here, point events representing flow gauges along river reaches areshown.

A12

3

B45

6

0

55

0

37

12 A1

30

47

9

35

A3

B1

B2

GAUGE_ID

B456

B456

A123

A123

A123

REACH MP

A2

GAUGES

Route identifier

Measure location

5 13153017

5225

SALMONSTEELHEAD

SALMONSTEELHEAD

SPECIESTMP

B456A123A123A123

REACH FMP

25

HABITAT

A12

3

B45

6

0

55

0

37

Route identifier

Measure location

Events are located along a route using their route location information.Here, line events representing fish habitats along river reaches are shown.

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LINEAR REFERENCING 45

Within an organization, there may be many departments that useroute event data. Each department will collect event data usingthe route measurement system that best suits its needs. Within astate DOT, for example, the safety department might collectaccident location events using a reference marker system ofmeasurement, while the maintenance department might collectpavement quality information using a mile post system ofmeasurement. Each system is known as a linear referencingmethod.

A route in ArcGIS can only store one system of measurement. Inmany organizations, therefore, there is a need to maintain multipleroute feature classes—one for each linear referencing method.

Linear referencing and topology

The ability to manage these feature classes in an integratedfashion is critical.

In GIS technology, topology is the model used to describe howfeatures share geometry. It is also the mechanism for establishingand maintaining topological relationships between features andfeature classes. ArcGIS implements topology through a set ofvalidation rules that define how features share geographic spaceand a set of editing tools that work with features that sharegeometry in an integrated fashion.

By defining a topology, organizations can achieve the dataintegration between route feature classes they require. For moreinformation on topology, see Building a Geodatabase andEditing in ArcMap.

A topology facilitates the use of multiple linear referencing methods.

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IN THIS CHAPTER

47

Creating route data 4• Route data

• Creating route feature classes

• Creating routes from existing lines

• Calibrating routes with points

• Migrating route data to ageodatabase

Before embarking on any linear referencing project, you will need routedata. This data may not exist, may exist but without the appropriate measuresystem defined, or may exist in a format you do not wish to use.

ArcGIS supports routes in three formats: coverage, shapefile, andgeodatabase. ArcCatalog and ArcToolbox provide you with the toolsnecessary to create, calibrate, and migrate route data from one supportedformat to another.

In this chapter, you will learn how to:

• Create new route feature classes.

• Create route feature classes from existing lines.

• Calibrate routes using points.

• Migrate routes from one format to another.

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48 LINEAR REFERENCING IN ARCGIS

Route data

A route is a linear feature that has a unique identifier andmeasurement system stored with it. Routes can be stored incoverages, shapefiles, and personal and ArcSDE® geodatabases.

ArcCatalog and ArcToolbox contain tools for creating route datain shapefiles and geodatabases. In addition to the ability to createempty route feature classes for later digitizing or importing, thereare tools for creating routes by merging existing line features,calibrating route data with points, and migrating route data fromone format to another. When a route feature class is stored in ageodatabase, there are special storage considerations.

There are tools for creating coverage route data, but they will notbe discussed in this chapter. ArcInfo Workstation remains thebest place to create coverage route data. For more information oncreating coverage route data, see the ArcInfo Workstation onlineHelp.

Merging linear features to create routes

It is possible to create routes by merging linear features thatshare a common identifier. There are two scenarios for how theroute measures will be set:

• Measure values for the input features are not known.

• Measure values for the input features are known.

Measure values are not known

When route measure values are not known, they can begenerated either by accumulating the digitized length or byaccumulating a numeric attribute value of the input features. Ifyou choose to use digitized length, the units of the output routemeasures will be the same as the output coordinate system (feet,meters, etc.). If you choose to use a numeric attribute, the outputroute measures can be any units you want.

When routes are created in this manner, you control the directionmeasures are assigned to the routes by specifying the coordinatepriority of the starting measure. The coordinate priority can beupper left, upper right, lower left, or lower right. These options aredetermined by placing the minimum bounding rectangle aroundthe input features that are going to be merged to create one route.

Routes can be stored in coverages, shapefiles, and geodatabase featureclasses.

geodatabase

coverage

shapefile

ArcInfo and ArcEditor

Polyline 1PolylinePolyline 1

1.11.20.9

MILESRKEY

210

OID Shape

1

OID = 0 1 2

PolylineM 1RKEY

0OID Shape

0

1.1

2.3

3.2

Measure values are obtained by accumulating the values in the MILESfield. Note that the digitized direction of the input features does not matterbecause a starting priority is given. In this example, the starting priority islower left.

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CREATING ROUTE DATA 49

Routes with multiple, disjointed parts are supported. A routerepresenting a road, for example, might have the same name oneither side of a river. For situations like this, you can choose toignore spatial gaps between parts when creating routes. If youchoose to ignore spatial gaps, route measures will be continuouswhen a disjointed route is created. If you want the spatial gapincorporated in the measures, the gap distance is the straight-linedistance between the endpoints of the parts. The units of the gapwill be that of the output coordinate system, which may or maynot be the same as the measure units.

Measure values are known

When measure data already exists as attributes of the input linearfeatures, it is possible to create routes that inherit this measureinformation. For example, two fields may exist that store from- andto-mile information.

When using this method, it is important to orient each input linearfeature in the direction of increasing measure to prevent routesthat have measures that do not always increase.

ArcInfo and ArcEditor

Polyline 1PolylinePolylinePolyline

11

1.10.60.60.9

MILESRKEY

3210

OID Shape

1

OID = 01

2

PolylineM 1RKEY

0OID Shape

0

1.11.7

3.2

3

1.7

2.3

0

1.12.1

3.6

1.7

2.7

When creating disjointed routes, you can choose to have the measuresbe continuous or discontinuous. In this example, the starting priority islower left.

Polyline 1PolylinePolyline 1

01.12.3

1.12.33.2

TO_MFR_MRKEY

210

OID Shape

1

OID = 0 1 2

PolylineM 1RKEY

0OID Shape

0

1.1

2.3

3.2

Measure values are obtained by using the values in the FR_M and TO_Mfields. Note that the digitized direction of the input features determines thedirection of the output route.

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50 LINEAR REFERENCING IN ARCGIS

The calibration process creates a new vertex for every point within thespecified tolerance. The measure at each new vertex will correspond tothe point’s measure value. You control whether the remaining vertices willhave their measure interpolated or extrapolated (see below).

Tolerance

0

9

22

32

40

?

?

?

?

?

5

15

30

34

5 1530

34

Calculating route measures using points

When route measures are inaccurate, events will not be locatedproperly. A route representing a highway, for example, might be10.5 miles long. A bend in the highway might have its measurevalue set to 6.1 miles. In reality, however, the bend in the highwayoccurs at mile 6.5. Events on this route, especially near the bend,will be located incorrectly.

It is possible to adjust route measures to correspond with knownmeasure locations using a procedure called calibration.Calibration adjusts route measures by reading measureinformation stored as an attribute in a point feature class. Eachpoint falls on the particular route it calibrates or within a giventolerance. Many points may be used to calibrate a single route.

During the calibration process, a new vertex is created where thecalibration points intersect the route. The measure value on thesenew vertices corresponds to the measure value stored as a pointattribute. The measure values on other preexisting route verticescan be interpolated and/or extrapolated.

Both whole and partial routes can be calibrated. You can chooseto interpolate between the input points, extrapolate before theinput points, extrapolate after the input points, or use anycombination of these three methods.

In order for the measure value on a vertex to be interpolated orextrapolated, a calibration ratio is needed. There are two ways thisratio can be determined. The first method uses the shortest pathdistance between the input points.

1.88

9.69

19.62

31.75

385 15

30

34

Measure value at v1 is extrapolated as follows: - distance (d1) between p1 and p2 is 14.31 - measure distance between p1 and p2 is 15-5 = 10 - calibration ratio is 14.31/10 = 1.431 - distance (d2) between p1 and v1 is 4.47

The measure value at v2 is interpolated as follows: - distance (d1) between p1 and p2 is 14.31 - measure distance between p1 and p2 is 15-5 = 10 - calibration ratio is 14.31/10 = 1.431 - distance (d3) between p1 and v2 is 6.71

The measure value at v3 is interpolated as follows: - distance (d4) between p2 and p3 is 11.628 - measure distance between p2 and p3 is 30-15 = 15 - calibration ratio is 11.628/15 = 0.775 - distance (d5) between p2 and v3 is 3.58

The measure value at v4 is interpolated as follows: - distance (d6) between p3 and p4 is 7.16 - measure distance between p3 and p4 is 34-30 = 4 - calibration ratio is 7.16/4 = 1.79 - distance (d7) between p3 and v4 is 3.13

The measure value at v5 is extrapolated as follows: - distance (d6) between p3 and p4 is 7.16 - measure distance between p3 and p4 is 34-30 = 4 - calibration ratio is 7.16/4 = 1.79 - distance (d8) between p4 and v5 is 7.16

0

9

22

32

405

15

30 34v1

v2 v3 v4

v5

p1

p2

p3 p4

d1

d3

d2

d4

d5

d6

d7

d8

4.47/1.431 = 3.125-3.12 = 1.88

6.71/1.431 = 4.695+4.69 = 9.69

3.58/0.775 = 4.6215+4.62 = 19.62

3.13/1.79 = 1.7530+1.75 = 31.75

7.16/1.79 = 434+4 = 38

The calibration ratio can be determined using the shortest path distancebetween the input points.

ArcInfo and ArcEditor

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CREATING ROUTE DATA 51

The second method uses the existing measure distance betweenthe input points. This second method is useful when the lengthto measure ratio on the input route is not consistent and you areusing the calibration process to fine-tune a route’s measures.

When calibrating disjointed routes, you may choose to ignore thedistance of the spatial gap between the parts. If you choose toignore spatial gaps, route measures will be continuous. If youwant the spatial gap incorporated in the measures, the gapdistance is the straight-line distance between the endpoints ofthe parts. The units of the gap will be that of the outputcoordinate system, which may or may not be the same as themeasure units. Ignoring spatial gaps is only a valid choice whenusing the shortest path distance method of calibration.

The measure value at v1 is extrapolated as follows: - old measure distance (d1) between p1 and p2 is 17.84-3.6 = 14.24 - new measure distance between p1 and p2 is 15-5 = 10 - calibration ratio is 14.24/10 = 1.424 - old measure distance (d2) between p1 and v1 is 3.6-0 = 3.6

The measure value at v2 is interpolated as follows: - old measure distance (d1) between p1 and p2 is 17.84-3.6 = 14.24 - new measure distance between p1 and p2 is 15-5 = 10 - calibration ratio is 14.24/10 = 1.424 - old measure distance (d3) between p1 and v2 is 9-3.6 = 5.4

The measure value at v3 is interpolated as follows: - old measure distance (d4) between p2 and p3 is 29.2-17.84 = 11.36 - new measure distance between p2 and p3 is 30-15 = 15 - calibration ratio is 11.36/15 = 0.757 - old measure distance (d5) between p2 and v3 is 22-17.84 = 4.16

The measure value at v4 is interpolated as follows: - old measure distance (d6) between p3 and p4 is 34.88-29.2 = 5.68 - measure distance between p3 and p4 is 34-30 = 4 - calibration ratio is 5.68/4 = 1.42 - old measure distance (d7) between p3 and v4 is 32-29.2 = 2.8

The measure value at v5 is extrapolated as follows: - old measure distance (d6) between p3 and p4 is 34.88-29.2 = 5.68 - measure distance between p3 and p4 is 34-30 = 4 - calibration ratio is 5.68/4 = 1.42 - old measure distance (d8) between p4 and v5 is 40-34.88 = 5.12

0

9

22

32

40

5/3.6

15/17.84

30/29.2 34/34.88v1

v2 v3 v4

v5

p1

p2

p3 p4

d1

d3

d2

d4

d5

d6

d7

d8

2.47

8.79

20.49

31.97

37.615 15

30

34

3.6/1.424 = 2.535-2.53 = 2.47

5.4/1.424 = 3.795+3.79 = 8.79

4.16/0.757 = 5.4915+5.49 = 20.49

2.8/1.42 = 1.9730+1.97 = 31.97

5.12/1.42 = 3.6134+3.61 = 37.61

The calibration ratio can be determined using the measure distancebetween the input points.

ArcInfo and ArcEditor

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52 LINEAR REFERENCING IN ARCGIS

Special considerations for geodatabases

When you create a new standalone feature class or a featureclass in a new feature dataset, you must specify a spatialreference. The spatial reference for a feature class contains itscoordinate system—for example, geographic, UTM, and StatePlane—and the spatial domains—x, y, z, and m. For moreinformation on spatial references, see Building a Geodatabase.

You need to choose appropriate x, y, m, and perhaps z domainswhen creating route feature classes because they describe themaximum extent to which data can grow. For example, if you createa feature class with a minimum m value of 0 and a precision of1,000, none of the routes in the feature class will be able to havemeasures that are less than 0. Further, all route measures will beaccurate to three decimal places (a precision of 1,000 impliesaccuracy to three decimal places). Similar considerations apply tothe x, y, and z domains.

All feature classes in a feature dataset share a common spatialreference. This means that the domains are shared as well. Theexception to the rule is the m domain. Feature classes within thesame feature dataset can have a different m domain. This is toaccount for the fact that different route feature classes mighthave different units of measure (for example, feet, meters, andmiles). Whenever you create a route feature class in an existingfeature dataset, you should always set an appropriate m domain.

Choosing an appropriate m domain

However route data is created, one important goal is to preservemeasure accuracy. When data is stored in a geodatabase, allnumeric values are converted to integers. Because of this,converting data to and from integer space can sacrifice measureaccuracy if inappropriate m domain values are used.

To determine an appropriate m domain, you need to know boththe route storage units and the route measure units. The routestorage units reflect how accurately the route data was collected.For example, route measure data may be accurate to the foot,meter, or even decimeter level.

The route measure units refer to the units in which routelocations are reported. For example, they may be feet, meters,miles, and so on. Route measure units have nothing to do withhow accurately the route’s data was collected and stored.

Precision is the multiplier that scales measure units into storageunits. The lowest precision value you should use is the routemeasure units divided by the storage units. For example, if theroute measure units are kilometers and there is meter-levelaccuracy, the lowest precision value you should use is 1,000.Further, if the route measure units are miles and there is accuracyto the foot, the lowest precision you should use is 5,280.

Suppose you have a route feature class in which the routemeasure units are kilometer and the route storage units areaccurate to the meter level. Further suppose that this routefeature class has an m domain in which the measure minimumis -1,000 and the measure precision is 100, which is incorrect. If anew route is created in this feature class and its measure valuesare set to range between 0 and 1,324.526, the following diagramillustrates that the accuracy of the route’s measures is notmaintained when the route is stored and subsequently retrievedfrom the geodatabase. Note that the same process happens forevery measure value on the route.

If the route feature class has an appropriate m precision of 1,000,the measure accuracy of the route is maintained on a round-trip tothe geodatabase.

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CREATING ROUTE DATA 53

It is often a good idea to use a precision that is greater than thecalculated value to allow for the future storage of more accuratedata. In most cases this is not a problem, but be aware that thereis a trade-off between precision and the range of measure inwhich values can be stored. The higher the precision value that isused, the smaller the range of measure values that routes canhave.

Grid size

Another consideration regarding geodatabase feature classes isthe grid size of the spatial index. The spatial index is used toquickly locate features that match the criteria of a spatial search.

For most data, only a single grid size is required. Because featuresize is an important factor in determining an optimum grid size,data that contains features of very different sizes may requireadditional grid sizes so larger features can be queried faster.Feature classes in ArcSDE geodatabases may have up to threegrid sizes. Each grid size must be at least three times the previousgrid size. For a more detailed discussion of spatial indexes andgrid sizes, see the ArcSDE Administration Guide PDF file and theArcSDE Configuration and Tuning Guide for <DBMS> PDF file.

When creating a new route feature class, the default grid size is1,000. This value should be changed. When merging lines tocreate routes, calibrating route measures with points, or migratingroute data to a geodatabase, the default grid size is in the units ofthe input coordinate system. If you change the output coordinatesystem, you need to set a new grid size so it is in the units of theoutput coordinate system. For example, if the input feature classhas a geographic coordinate system and its units are decimaldegrees, the default grid size may be 10. If the output coordinatesystem is set to be UTM meters, the default grid size should beset to a value suitable for new units, such as 10,000.

If an inappropriate grid size is used, an error stating that the gridsize is too small may occur when storing features into a featureclass, or you may experience poor spatial search performance.

1324.526

Subtract offset(1324.526 - (-100))

Multiply by precision(1424.526 * 100)

142453(Value stored inGeodatabase)

Divide by precision(142453 / 100)

Add offset(1424.53 + (-100))

1324.530

When an incorrect measure precision is used, measure accuracy can belost on a round-trip to the geodatabase.

1324.526

Subtract offset(1324.526 - (-1000))

Multiply by precision(2324.526 * 1000)

2324526(Value stored inGeodatabase)

Divide by precision(2324526 / 1000)

Add offset(2324.526 + (-1000))

When a correct measure precision is used, measure accuracy ismaintained on a round-trip to the geodatabase.

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54 LINEAR REFERENCING IN ARCGIS

Creating routefeature classesYou create new route featureclasses in ArcCatalog. Whencreating a route feature class,you must define the geometryfield’s geometry type to bepolyline and indicate that it beable to store measure values.You also need to add a routeidentifier field. This fielduniquely identifies each route.

When creating a route featureclass in a geodatabase, youmust also define the spatialreference. Note that if you arecreating a feature class in apreexisting feature dataset, youneed only set the m domain.This is because all featureclasses in a feature datasetshare a common spatialreference, which was createdwhen the feature dataset wascreated. The m domain, how-ever, can be different for eachfeature class. This is becauseroute feature classes in afeature dataset often havedifferent units of measure—forexample, feet, meters, and miles.

When creating a shapefile thatwill store routes, you maychoose to define the coordinatesystem later. It will be classifiedas Unknown until that time. �

Creating a newstandalone feature classto store routes

1. Right-click the geodatabase,in the Catalog tree, in whichyou want to create a newroute feature class, point toNew, then click FeatureClass.

2. Type a name for the newfeature class. To create analias for this feature class,type the alias.

3. Click Next. �

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CREATING ROUTE DATA 55

See Also

For details about using configura-tion keywords with ArcSDE, see theArcSDE Configuration and TuningGuide for <DBMS> PDF file.

Tip

Using another featureclass as a templateWhen creating a new feature classin a geodatabase, you can useanother feature class as a template.Click Import, navigate to thefeature class whose field definitionsyou want to copy, then click OK.You can edit the field names andtypes as required.

The process of defining ashapefile’s attributes is separatefrom creating the shapefileitself. To create the routeidentifier plus all other fields,you need to right-click in theCatalog tree and click Propertiesto define the attributes. Notethat because a shapefile mustcontain at least one field, theinteger field Id has already beenadded. Add the appropriatefields to the shapefile, thendelete the default field.

If your geodatabase does notuse ArcSDE, skip to Step 5.

4. Click Use configurationkeyword and click thekeyword you want to use ifyou want to create a featureclass with a custom storagekeyword.

5. Click Next.

6. Click the SHAPE field in theField Name column.

7. Click the field next to Aliasand type the alias to createan alias for the SHAPE field.

8. Click the field next to AllowNULL values, click thedropdown arrow, then clickNo to prevent null shapesfrom being stored.

9. Click the field next to Geom-etry Type, click the dropdownarrow, then click Line for thefeature’s type.

10. Click the fields next to thegrids and type the grid valueto set the spatial index gridparameters for the featureclass.

11. Click the field next toContains M values, click thedropdown arrow, then clickYes.

12. Click the Spatial ReferenceProperties button. �

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56 LINEAR REFERENCING IN ARCGIS

Tip

PrecisionThe size of a spatial domain (XY, Z,or M) is dependent on the value ofprecision. When the precision ischanged, the maximum value forthe domain will change to fit thesize of the extent. Similarly, whenthe maximum value is changed, theprecision will change to fit theextent.

See Also

For details on how to create a newcoordinate system and forimportant information aboutspatial references and how theyaffect your data, see Building aGeodatabase.

13. Click Select, Import, or Newto set the feature class’scoordinate system.

14. Click the X/Y Domain tab.

15. Type the Min X, Min Y, andPrecision values for the XYDomain.

16. Click the M Domain tab.

17. Type the Min, Max, andPrecision values for the MDomain.

18. Click OK. �

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CREATING ROUTE DATA 57

Tip

Creating a route featureclass in an existing featuredatasetThe process of creating a routefeature class in an existing featuredataset is similar to that of creatinga standalone route feature class.Steps 13 through 15 of ‘Creating anew standalone feature class tostore routes’ are not valid becauseall feature classes in a featuredataset share a common spatialreference, which was created whenthe feature dataset was created andcannot be changed. The exceptionis the m domain, which you shouldalways set.

Tip

Creating an index on theroute identifier fieldIt is recommended that you createan attribute index on the routeidentifier field. This index willimprove dynamic segmentationperformance.

See Also

For more information on creatinga feature class in a feature dataset,see Building a Geodatabase.

See Also

For more information on creatinga field index in a feature class, seeBuilding a Geodatabase.

19. Add the route identifier fieldto the feature class.

Click in the next blank row inthe Field Name column andtype a name.

20. Click in the Data Typecolumn next to the newfield’s name and click itsdata type.

21. Either click the property inthe dropdown list or type theproperty to set other proper-ties specific to the type offield.

22. Repeat steps 19 through 21until all the feature class’sfields have been defined.

23. Click Finish.

��

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58 LINEAR REFERENCING IN ARCGIS

Creating a new shapefileto store routes

1. Right-click the folder, in theCatalog tree, in which youwant to create a newshapefile, point to New, thenclick Shapefile.

2. Type a name for the newshapefile.

3. Click the Feature Typedropdown arrow and clickPolyline.

4. Check Coordinates willcontain M values.

5. Click Edit to define theshapefile’s coordinatesystem.

When you are finishedsetting the shapefile’scoordinate system (Step 7),you will be returned to thisdialog box.� �

See Also

For more information on creatingshapefiles, see Using ArcCatalog.

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CREATING ROUTE DATA 59

Tip

Creating an index on theroute identifier fieldIt is recommended that you createan attribute index on the routeidentifier field. This index willimprove dynamic segmentationperformance.

See Also

For more information on creatinga field index in a shapefile, seeUsing ArcCatalog.

6. Click Select, Import, or Newto set the shapefile’s spatialreference.

7. Click OK.

8. Click OK.

9. Add the route identifier fieldto the feature class. Right-click the feature class in theCatalog tree and clickProperties. �

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60 LINEAR REFERENCING IN ARCGIS

Tip

Deleting the default Id fieldThe integer field Id is a default fieldand can be deleted once anotherfield has been added to theshapefile.

10. Click the Fields tab.

11. Click the next blank row inthe Field Name column andtype in a name of the routeidentifier field.

12. Click in the Data Typecolumn next to the newfield’s name and click itsdata type.

13. Click in the Field Propertieslist and type the propertiesfor the new field.

14. Repeat steps 9 through 12until all the shapefile’s fieldshave been defined.

15. Click OK.

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CREATING ROUTE DATA 61

1. Navigate to the LinearReferencing toolbox in theToolbox tree and double-click Create Routes Wizard.

2. Navigate to the input featureclass or type in the name andlocation of the input featureclass.

3. Click the Route IdentifierField dropdown arrow andclick the route identifier field.

4. Click Next.

5. Click how you want theoutput route measures to beobtained.

6. Uncheck Ignore spatial gapsif you do not want spatialgaps to be ignored whenmeasures are being set.

This option will not beavailable if you chose Usetwo fields from the inputfeature class in Step 5.

7. Click Next.

If you chose Use two fieldsfrom the input feature class inStep 5, skip to Step 10.��

Creating routesfrom existinglinesYou create routes from existinglines in ArcToolbox. Input linearfeatures that share a commonidentifier are merged to create asingle route.

The input feature classes canbe any supported format. Thisincludes coverage, shapefile,personal and enterprisegeodatabase, and CAD data.

As the input linear features aremerged, the route measures aredetermined in one of threeways:

• The geometric lengths of theinput features are used toaccumulate the measures.

• A value stored in a measurefield is used to accumulatethe measures.

• The values stored in from-and to-measure fields areused to set the measures.

With the first two options, youchoose whether the outputroutes will have continuousmeasures when there aredisjointed parts. �

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62 LINEAR REFERENCING IN ARCGIS

Also with the first two options,you control the directionmeasures are assigned to theroutes by specifying thecoordinate priority of thestarting measure. The coordi-nate priority can be upper left,upper right, lower left, or lowerright. These options aredetermined by placing theminimum bounding rectanglearound the input features thatare going to be merged to createone route.

It is possible to specify a queryto limit the number of linearfeatures that are used to createroutes.

The output routes can bewritten to a shapefile or ageodatabase feature class.

If your input features have adefined projection, the CreateRoutes Wizard will preserve thisprojection. You can choose tochange the projection informa-tion for the output, in whichcase the features will automati-cally be projected. Note thatyou cannot change the projec-tion if you are writing to anexisting feature dataset.

When writing to a geodatabase,you should always set the mdomain. A default m domain willbe calculated for you, but thismight not accurately reflectyour data. �

8. Click the coordinate priorityappropriate for your data.

9. Click Next.

10. Click where you want towrite the output route featureclass.

11. Click Next.

If you chose Shapefile, skipto Step 25.

12. Navigate to the database ordatabase connection intowhich you want to write thenew route feature class, ortype its name and location.

13. Click the dropdown arrowand click the feature datasetto which you want to migrateif you want to migrate to anexisting or new featuredataset.

Type the name of the newfeature dataset if you want tomigrate to a new featuredataset.

Leave it blank if you want tomigrate to a standalonefeature class.

14. Type a name for the newfeature class.

15. Click Change Settings.

When finished setting thefeature class’s coordinatesystem (Step 24), you willreturn to this dialog box. �

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CREATING ROUTE DATA 63

See Also

For more information on adding acommand to a context menu, seeUsing ArcCatalog.

Tip

Create Routes WizardYou can add the Create RoutesWizard to ArcCatalog context menuchoices.

See Also

For details on how to create a newcoordinate system and forimportant information aboutspatial references and how theyaffect your data, see Building aGeodatabase.

When writing to a geodatabase,you should examine the gridsize for the output spatial index.If your input route feature classis already in a geodatabase, thesuggested grid size will be thesame as the input. In all othercases, a default will be approxi-mated.

16. Click Change.

17. Click Select, Import, or Newif you want to change theoutput coordinate system.

These are not availablewhen migrating to anexisting feature dataset.

18. Click the X/Y Domain tab ifyou wish to change the MinX, Min Y, and Precisionvalues for the XY Domain.

This is not possible whencreating a feature class in anexisting feature dataset. �

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64 LINEAR REFERENCING IN ARCGIS

Tip

PrecisionThe size of a spatial domain (XY, Zor M) is dependent on the value ofprecision. When the precision ischanged, the maximum value forthe domain will change to fit thesize of the extent. Similarly, whenthe maximum value is changed, theprecision will change to fit theextent.

19. Click the M Domain tab.

20. Type the Min, Max, andPrecision values for the MDomain.

21. Click OK.

22. Click the Grid Size tab andtype the grid size or sizes ifyou want to set the spatialindex grid parameters for thefeature class.

Only one index grid is usedin personal geodatabases,while ArcSDE geodatabasesuse up to three. �

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CREATING ROUTE DATA 65

See Also

For more information aboutconfiguration keywords withArcSDE, see the ArcSDE Configu-ration and Tuning Guide for<DBMS> PDF file.

If your geodatabase doesnot use ArcSDE, skip toStep 25.

23. Click the Config Keywordtab, click Use configurationkeyword, then type thekeyword you want to use ifyou want to create a featureclass with a custom storagekeyword.

24. Click OK.

Skip to Step 26.

25. Navigate to the folder intowhich you want to write thenew shapefile or type itsname and location.

26. Click Next. ��

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66 LINEAR REFERENCING IN ARCGIS

27. Click whether you want touse all features or only thosefeatures that satisfy a query.

28. Click Next.

29. Review your settings andclick Finish.

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CREATING ROUTE DATA 67

1. Navigate to the LinearReferencing toolbox in theToolbox tree and double-click Calibrate RoutesWizard.

2. Navigate to the route featureclass, or type in the nameand location of the routefeature class.

3. Click Exclude features withno calibration points from theoutput feature class ifapplicable.

4. Click the Route IdentifierField dropdown arrow andclick the route identifier field.

5. Click Next.

6. Navigate to the point featureclass, or type in the nameand location of the pointfeature class.

7. Click the Point Identifier fielddropdown arrow and clickthe point identifier field.

8. Click the Measure fielddropdown arrow and clickthe measure field.

9. Type a tolerance.

10. Click Next. �

Calibratingroutes with pointsYou calibrate routes with pointsin ArcToolbox. Whencalibrating, you can choose toexclude routes without anyassociated calibration pointsfrom the output.

The calibration of whole orpartial routes is possible.

Route measures can be updatedusing the shortest pathdistance between the calibra-tion points or using the existingmeasure distance between thepoints. In most applications,using the shortest pathdistance between the calibra-tion points will be sufficient.Calibrating by measure distanceshould be used on data forwhich the length to measureratio is not consistent atvarious locations along theinput routes.

When calibrating using theshortest path distance, you canchoose whether the outputroutes will have continuousmeasures when there aredisjointed parts.

A tolerance can be specified tolimit how far a calibration pointcan be from a route. Pointsoutside the tolerance will not beused by the calibration process.The tolerance is expressed �

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68 LINEAR REFERENCING IN ARCGIS

in the same units as the routefeature class’s coordinatesystem.

It is possible to calibrate linearfeatures without existingmeasures. In this situation, theinput linear features will bemerged (if necessary) based onthe route identifier field beforethe calibration process begins.This initial step is not per-formed if the input featuresalready have measure values.

The input feature classes canbe any supported format. Thisincludes coverage, shapefile,personal and enterprisegeodatabase, and CAD data.

It is possible to specify a queryto limit the number of pointsthat are used to calibrate.

The output routes can bewritten to a shapefile or ageodatabase feature class.

If your input route featureshave a defined projection, theCalibrate Routes Wizard willpreserve this projection. Youcan choose to change theprojection information for theoutput, in which case thefeatures will automatically beprojected. Note that you cannotchange the projection if you arewriting to an existing featuredataset. �

11. Uncheck any interpolation orextrapolation options you donot want. They are allchecked by default.

12. Click the calibration methodyou want to use.

13. Uncheck Ignore spatial gapsif you do not want gapsignored.

14. Click Next.

15. Click where you want towrite the output route featureclass.

If you chose Shapefile, skipto Step 30.

16. Click Next.

17. Navigate to the database ordatabase connection intowhich you want to write thenew route feature class, ortype its name and location.

18. Click the dropdown arrowand click the feature datasetif you want to migrate to anexisting feature dataset.

Type the name of the newfeature dataset if you want tomigrate to a new featuredataset.

Leave it blank if you want tomigrate to a standalonefeature class.

19. Type a name for the newfeature class.

20. Click Change Settings. �

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CREATING ROUTE DATA 69

See Also

For details on how to create a newcoordinate system and forimportant information aboutspatial references and how theyaffect your data, see Building aGeodatabase.

21. Click Change.

22. Click Select, Import, or Newif you want to change theoutput coordinate system.

These are not availablewhen migrating to anexisting feature dataset.

23. Click the XY Domain tab ifyou wish to change the MinX, Min Y, and Precisionvalues for the XY Domain.

This is not possible whencreating a feature class in anexisting feature dataset. �

If your input points have aprojection different from theroutes, they will be projected tothat of the routes before thecalibration process begins.

When writing to a geodatabase,you should always set the mdomain. A default m domain willbe calculated for you, but thismight not accurately reflectyour data.

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70 LINEAR REFERENCING IN ARCGIS

See Also

For more information on adding acommand to a context menu, seeUsing ArcCatalog.

Tip

Calibrate Routes WizardYou can add the Calibrate RoutesWizard to ArcCatalog context menuchoices.

�24. Click the M Domain tab.

25. Type the Min, Max, andPrecision values for the MDomain.

26. Click the Grid Size tab andtype the grid size or sizes ifyou want to set the spatialindex grid parameters for thefeature class.

Only one index grid is usedin personal geodatabases,while ArcSDE geodatabasesuse up to three. �

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CREATING ROUTE DATA 71

See Also

For more information aboutconfiguration keywords withArcSDE, see the ArcSDE Configu-ration and Tuning Guide for<DBMS> PDF file.

If your geodatabase doesnot use ArcSDE, skip toStep 29.

27. Click the Config Keywordtab, click Use configurationkeyword, then type thekeyword you want to use ifyou want to create a featureclass with a custom storagekeyword.

28. Click OK.

Skip to Step 30.

29. Navigate to the folder intowhich you want to write thenew shapefile or type itsname and location.

30. Click Next. �

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72 LINEAR REFERENCING IN ARCGIS

31. Click whether you want touse only the point featuresthat satisfy a query.

32. Click Next.

33. Review your settings andclick Finish.

!

"

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CREATING ROUTE DATA 73

Migrating routedata to ageodatabaseArcCatalog and ArcToolboxeach contain tools to migrateroute data from one supportedformat to another. During theconversion, all measure valuesare preserved. The example inthis section converts a cover-age route system to ageodatabase feature class.

When migrating to ageodatabase, you can create astandalone feature class, afeature class in a new featuredataset, or a feature class in anexisting dataset.

If your input route featureshave a defined projection, thedata conversion tools willpreserve this projection. Youcan choose to change theprojection information for theoutput, in which case thefeatures will automatically beprojected. Note that you cannotchange the projection if you arewriting to an existing featuredataset. �

Migrating a coverageroute system to ageodatabase

1. Right-click the coverageroute system, in the Catalogtree, that you want tomigrate, point to Export, thenclick Coverage toGeodatabase.

2. Navigate to the database ordatabase connection towhich you want to migrate, ortype its name and location.

3. Click the dropdown arrowand click the feature datasetto which you want to migrateif you want to migrate to anexisting or new featuredataset.

Type the name of the newfeature dataset if you want tomigrate to a new featuredataset.

Leave it blank if you want tomigrate to a standalonefeature class.

4. Type a name for the newfeature class.

5. Click Change Settings.

When you are finishedsetting the spatial reference(Step 13), you will bereturned to this dialog box. �

Tip

Coverage to GeodatabaseThe Coverage to Geodatabase toolis also available in ArcToolbox.

���

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74 LINEAR REFERENCING IN ARCGIS

See Also

For more information on migratingexisting data to a geodatabase, seeBuilding a Geodatabase.

A default m domain will becalculated for you. If yoursource feature class is acoverage or shapefile, youshould consider changing thedefault. This is because thedefault is calculated by simplyexpanding the minimum andmaximum measure values fromthe input by some factor. Thiscan result in an m domain with aprecision value that is artifi-cially high. A high precisionlimits the range of measurevalues that can be stored in thefuture.

The data conversion tools willsuggest a default grid size forthe output spatial index. Thissuggested grid size is only anapproximation.

6. Click Change.

7. Click Select, Import, or New ifyou want to change theoutput coordinate system.

This is not possible whenmigrating to an existingfeature dataset.

8. Click the X/Y Domain tab ifyou wish to change the MinX, Min Y, and Precisionvalues for the XY Domain.

This is not possible whenmigrating to an existingfeature dataset. �

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CREATING ROUTE DATA 75

�9. Click the M Domain tab.

10. Type the Min, Max, andPrecision values for the MDomain.

11. Click the Grid size tab andtype the grid size or sizes ifyou want to set the spatialindex grid parameters for thefeature class.

Only one index grid is usedin personal geodatabases,while ArcSDE geodatabasesuse up to three. �

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76 LINEAR REFERENCING IN ARCGIS

Tip

Corrected field namesDifferent databases allow differentfield names. The data conversiontools automatically make anynecessary changes. You can reviewthese changes and choose to acceptthem or assign your own names.

See Also

For more information on datamapping, see Building aGeodatabase.

See Also

For more information aboutconfiguration keywords withArcSDE, see the ArcSDE Configu-ration and Tuning Guide for<DBMS> PDF file.

12. Click the Item names tab ifyou want to review orchange the field mappings.

Make any necessarychanges to the CorrectedFields and Delete Fieldcolumns.

If your geodatabase doesnot use ArcSDE, skip toStep 14.

13. Click the Keyword tab, clickUse configuration keyword,then type the keyword youwant to use if you want tocreate a feature class with acustom storage keyword.

14. Click OK.

15. Click OK.

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IN THIS CHAPTER

77

Displaying and querying routes and events 5• The route identifier field

• Querying route data

• Hatching

• Displaying hatches

• Manipulating the text on hatches

• Hatch styles

• Route measure anomalies

• Dynamic segmentation

• Adding route events

Geographic data is represented on a map as a layer. Route and event data isno different. ArcMap provides you with the tools to add route and eventdata to a map as a layer. ArcMap also provides you with many tools forsymbolizing and labeling route and event layers in a wide variety of ways.

Once your route and event data have been added to a map, you can gainmuch insight by just looking at it. You may, however, want to discoverspatial relationships that are not apparent to the naked eye. ArcMapprovides you with a number of tools to find answers to questions such asWhere is...?, What is...?, Where is the closest...?, What’s inside...?, andWhat intersects...? In addition to these tools, ArcMap provides you withtools designed specifically for linear referencing data. With these additionaltools, you can:

• Find route and measure information by pointing at your map.

• Find route locations on a map by providing route and measureinformation.

For more information on displaying and querying your data, refer to UsingArcMap.

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The routeidentifier fieldArcMap is aware when data hasbeen added to the map. Whenroute data is added, ArcMapexposes some extra propertiesfor the new layer. One of thesenew properties is the routeidentifier field.

The route identifier uniquelyidentifies each route within afeature class. The route identi-fier field can be any numeric orcharacter field in your routefeature class.

Setting the route identifier fieldsaves steps when using many ofthe linear referencing anddynamic segmentation dialogboxes and wizards in ArcMap.

Setting the routeidentifier field

1. Right-click the layer, in thetable of contents, that youwant to set the route identifierfield for and click Properties.

2. Click the Routes tab.

3. Click the Route Identifierdropdown arrow and click thefield that is to be used as theroute identifier.

4. Click OK.

Tip

Saving the route identifierfieldIf the layer is saved as a layer file(.lyr), the route identifier field issaved as well.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 79

Adding the Identify RouteLocations tool

1. Click Customize from theArcMap Tools menu.

2. Click the Commands tab.

3. Click Linear Referencing inthe Categories list.

4. Drag the Identify RouteLocations tool to the toolbarof your choice (e.g., the Toolstoolbar).

5. Click Close.

Querying routedataA lot of information can bederived from a map by justlooking at it. There are times,however, when you need toknow more. Because of this,ArcMap provides you with thetools for querying your maps in awide variety of ways. In additionto the standard suite of mapquery tools, you can also findand identify route locations.

See Also

For more information on queryingmaps or adding commands to atoolbar or menu, see UsingArcMap.

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Identifying routelocations

1. Click the Identify RouteLocations tool.

2. Click the map in which youwant route and measureinformation.

Tip

Route Identifier fieldThe values displayed on thebranches of the route locationstree correspond to the values in theRoute Identifier field. See ‘Settingthe route identifier field’ in thischapter.

Tip

Layer dropdown listUse the Layer dropdown list toidentify route locations fromspecific layers only.

Tip

The Identify RouteLocations tool is notenabledThe Identify Route Locations toolwill not be enabled when there areno route layers in the map.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 81

Labeling an identifiedroute location with a textgraphic

1. Right-click on a found routelocation and click Label routelocation.

See Also

When you draw or label a routelocation, ArcMap default symbolproperties are used. For moreinformation on ArcMap defaultsymbol properties, see UsingArcMap.

Tip

Controlling the text of theroute locationWhen a route location is labeled,the text comes from two sources.The route identifier reflects thename of the layer’s route identifierfield. The measure reflects thedescription that is displayed on theright panel of the Identify RouteLocations dialog box.

Tip

Changing what informationis displayedRight-click anywhere on the rightpanel of the Identify RouteLocations dialog box to expose acontext menu that allows you tocontrol which route locationinformation is displayed.

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Finding a route location

1. Click the Find tool on theArcMap Tools toolbar.

2. Click the Route Locationstab.

3. Click the Route Referencedropdown arrow and click thelayer that is the routereference.

4. Optionally, click the LoadRoutes button.

5. Click the Route dropdownarrow and click the route.

Alternatively, type the routeidentifier in the Routedropdown list.

6. Click whether the routelocation will be point or line.

7. Type the route measureinformation.

8. Click Find.

9. Right-click the found routelocation and explore thecontext choices available toyou.

Tip

Route identifier fieldThe Find dialog box pays attentionto the route identifier field. If youhave not set the route identifierfield, then you will need to clickthe Route Identifier dropdownarrow and click the field to be usedfor the route identifier betweenSteps 3 and 4. See ‘Setting theroute identifier field’ in thischapter.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 83

Hatching

Hatching is a type of labeling that is designed to post and labelhatch marks or symbols at a regular interval along measuredlinear features. Hatching can be used for both distance-based andnondistance-based measures. Distance-based measures includekilometers, miles, feet, and meters. Nondistance-based measuresinclude seismic shot point numbers where measure valuesgenerally increase in even intervals based on some nominaldistance.

0 cm 1 2 3 4 5 6

In this example, the ruler represents a hatch class. The interval of thehatches is 0.1 cm (1 mm). There are three hatch definitions. Eachdefinition is placed at a multiple of the hatch interval—10, 5, and 1,respectively. Some hatch definitions are labeled, while others are not.

Hatching can be used in applications with either distance-based ornondistance-based measures.

Hatching concepts

To display hatches on a layer, you must define one or more hatchclasses for the features you wish to hatch. Each hatch class iscomposed of one or more hatch definitions.

The easiest way to understand hatch classes and hatch definitionsis to use a ruler analogy. On a ruler, there is a series of verticallines, or hatches, separated by a regular interval. For example, ona centimeter (cm) ruler, the hatches are typically spaced everymillimeter (mm). One millimeter is 1/10 of a centimeter, so thehatch interval is 0.1.

Not all the hatches on a ruler are the same. Some are longer thanothers. Further, some have text, while others do not. On acentimeter ruler, the hatches placed at every millimeter (0.1 cm)are the shortest. The hatches placed at every 5 millimeters

(0.5 cm) are a bit longer. The hatches placed every 10 millimeters(1 cm) are the longest. The longest hatches typically have text toindicate the measure value.

In this example, the ruler is a hatch class. It is a container for thehatch definitions. There are three hatch definitions. Eachdefinition is placed at a multiple of the hatch interval. Thelongest hatches are placed at every 0.1 x 10 measure units. Thesecond longest hatches are placed at every 0.1 x 5 measure units.The shortest hatches are placed at every 0.1 x 1 measure units.

When placed on a map, hatch definitions within a single hatchclass will not draw on top of one another.

There is a special type of hatch definition known as an end hatchdefinition. An end hatch definition pays no attention to thespecified hatch interval. Rather, it simply draws hatch marks atthe low and high measure of a linear feature. For cases in whichhatches get placed too close together near the end of a feature, itis possible to specify an end hatch tolerance, which preventscertain hatches from drawing if they are within the tolerance(specified in measure units) of an end hatch.

Imagine that you have linear features whose measures are inmiles. You want to place a hatch every quarter of a mile. This is ahatch interval of 0.25. Further, you want the hatches placed atevery 0.25, 0.5, and 1 mile to look different (different length,different color). You want the hatches every mile to have text.Lastly, you want hatches at the ends of the feature. These endhatches are to look different than all other hatches and will have

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Hatching options

There are many ways in which you can control how hatchesappear on a map. The following illustrate some of the wayshatches can be manipulated.

All of the hatch definitions ina hatch class can be offset bythe same amount.Alternately, each individualhatch definition can have itsown offset.

Each hatch definition can bedisplayed to the left,centered on, or to the rightof a feature. When set tocenter, hatches will belabeled to the left of thefeature.

Hatching can start at ameasure location other thanthe low measure. Further,hatching can finish at alocation other than the highmeasure.

In the case in which afeature’s geometry hasmultiple parts, it is possibleto apply hatches to thefeature as a whole or to eachpart individually.

How hatching worksIn this example, the line is 4 miles long, and the hatchinterval is 0.25. To make hatches look like the following, fourhatch definitions are necessary.

Step 1: The hatch definition with the highest multiple of thehatch interval - HatchDef(4) - is placed first. Because an endhatch definition has been specified, no hatches are placed atthe ends even though the measure values are divisible bythe hatch interval.

Step 2: The hatch definition with the next highest multiple ofthe hatch interval - HatchDef(2) - is placed. These hatcheswill not overwrite hatches that have already been placed.

HatchDef(End) - placed only at route ends. Has text.

HatchDef(1) - placed every 0.25 miles (0.25 x 1). Does not have text.

1

0.0

HatchDef(2) - placed every 0.5 miles (0.25 x 2). Does not have text.

HatchDef(4) - placed every 1 mile (0.25 x 4). Has text.

31 20.0 4.0

Step 3: The hatch definition with the next highest multiple ofthe hatch interval - HatchDef(1) - is placed. These hatcheswill not overwrite hatches that have already been placed.

Step 4: The end hatch definition - HatchDef(End) - will beplaced.

31 2

31 2

31 20.0 4.0

31 2

31 2

0.0

4.0

31 20.0

4.0

2

1.0

3.0

31 2

0.0

4.0

31 20.0

4.0

31 2

0.0

4.0

31 20.0

4.0

1 2

0.0

5.0

3

1 2

0.0

5.0

2.5

2.5

3.5

4.5

4

text. The following example demonstrates conceptually howhatching works in this scenario.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 85

31 2

0.0

4.1

31 2

0.0

4.1

4

By default, the placement ofhatches is adjusted to thehatch interval. This meansthat in cases in which a line’slow measure is not divisibleby the interval, the first hatchwill be placed at the firstmeasure value that is divisible by the hatch interval. For example,a line whose measures range from 1.1 to 5.2 will have its firsthatch placed at 1.25 when the hatch interval is 0.25. Thisbehavior can be turned off. Note that end hatch definitions arenot affected by this setting and are not shown in this example.

In cases in which a feature’shigh measure is not divisibleby the hatch interval and anend hatch definition has beendefined, it is possible to gettwo hatches that are very close to or on top of one another. Toavoid this, it is possible to specify an end hatch tolerance, whichinforms the hatching algorithm to not place hatches when theyfall within the tolerance of the end hatch. The end hatch toleranceis specified in route measure units, and its value is typically set toa value that is less than the hatch interval.

Hatches are drawn perpendicular to the feature. It is possible tospecify a supplemental anglethat is added to thecalculated angle.

4.1

2.1

3.1

1.1

5.1

4.25

2.25

3.25

1.25

31 2

0.0

4.0

10.0

2 3 4.0

10.0

4.0

2

3

10.0

4.0

2

3

Hatch text is flipped as thedirection of the featurechanges. This is to makethe text more readable.This can be turned off sothe text is always orientedin the direction ofincreasing measure.

Hatches can also be placedonly at the route ends. In thiscase, it is not necessary tospecify a hatch interval.

Creating and managinghatches

Hatches are a feature layer property. As such, hatches are createdand managed on the Layer Properties dialog box.

The Hatches tab on the Layer Properties dialog box has threeviews: the hatch class view, the hatch definition view, and the endhatch definition view. The hatch class view is enabled when ahatch class is selected in the hatch tree. The hatch definition viewis enabled when a hatch definition is selected in the hatch tree.The end hatch definition view is enabled when an end hatchdefinition is selected in the hatch tree.

0.0

4.0

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86 LINEAR REFERENCING IN ARCGIS

Hatch Class view

Note that a hatch class is highlighted in the hatch tree.

The Hatch tab is only available forlinear feature layers with measures.

Hatch classes andhatch definitions canbe defined but notvisible.

The preview indicates what the hatches in thecurrently selected hatch class will look like.

Each hatch class canbe visible or notvisible. This is usefulwhen more than onehatch class has beendefined.

A hatch class alwayshas at least one hatchdefinition.

Right-clicking on ahatch class in the treedisplays a contextmenu.

Hatches can beimported fromanother layer in themap document orfrom a layer file (.lyr).

A single hatchinterval can beapplied to allfeatures, or differenthatch intervals canbe stored in a field.The hatch interval isalways specified inthe same units as theroute measures.

A hatch style can beapplied to theselected hatch class.

It is possible to limit thenumber of features that arehatched in each class byusing a SQL query.

The drawing of hatches atcertain scales can besuppressed.

Displays the Hatch PlacementOptions dialog box. These optionscontrol things such as the start andend measure ranges and whether allhatch definitions should be offset.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 87

Hatch Definition view

Note that a hatch definition is highlighted in the hatch tree.

The selected hatch definition ishighlighted using the ArcMapselection color.

A hatch definition’sname includes themultiple of the hatchinterval at which thehatches are to beplaced.

No two definitionswithin the same classcan have the samemultiple of the hatchinterval.

Right-clicking on ahatch definition in thetree displays a contextmenu.

A hatch definition is placed at a multiple of thehatch interval. The hatch interval is set on theHatch Class view.

Each hatch definition can be labeledwith the route measure.

A hatch definition canbe symbolized witheither a line ormarker symbol.

The line length andlateral offsetproperties arespecified in the unitsthat are set on theHatch PlacementOptions dialog box.

Displays the HatchOrientation dialogbox.

Displays the LabelSettings dialog box.

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End Hatch Definition view

Note that an end hatch definition is highlighted in the hatch tree.

An end hatchdefinition is a specialtype of hatchdefinition. Thesehatches are onlyplaced at the lineends.

Right-clicking on anend hatch definition inthe tree displays acontext menu.

If any of the hatchesfrom the other hatchdefinitions in thesame class are withinthe end hatchtolerance, they willnot be placed.

The end hatchtolerance is specifiedin route measureunits.

The selected end hatch definition ishighlighted using ArcMap selectioncolor.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 89

Hatch Placement Options dialog box

This dialog box is initiated by clicking the Hatch Placement button on the Hatch Class view. The settings made on this dialog box applyto all the hatch definitions that make up the selected hatch class.

The distance units apply to offsetsand hatch definition lengths. Theydo not refer in any way to the hatchinterval, which is specified in routemeasure units.

The default distance units are thesame as the active data frame’sdisplay units.

All hatch definitions in a class canbe offset by a value. A single offsetcan be applied to all features, ordifferent offsets can be stored in afield.

Note that it is possible to offsetindividual hatch definitions. This isdone on the hatch definition view.

It is possible to start hatching at avalue other than the lowestmeasure. A single value can beapplied to all features, or differentvalues can be stored in a field.These values are always specifiedin route measure units.

It is possible to finish hatching at avalue other than the highestmeasure. A single value can beapplied to all features, or differentvalues can be stored in a field.These values are always specifiedin route measure units.In some cases, the low measure of

a line is not exactly divisible by thehatch interval. The first hatchplaced will be adjusted to ameasure value that is divisible bythe hatch interval. This behaviorcan be turned off.

In some cases, a line might havemultiple parts. It is possible to applyall hatch settings to each partindividually.

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90 LINEAR REFERENCING IN ARCGIS

Hatch Orientation dialog box

This dialog box is initiated by clicking the Hatch Orientation button on the Hatch Definition view. The settings made on this dialog boxapply only to the currently selected hatch definition.

By default, a hatch’s text will onlybe the measure.

Alternatively, a prefix and/or a suffixcan be plotted before the measurevalues.

Lastly, label expressions can bebuilt using VBScript or JavaScript.

The precision of the value isdisplayed for the hatch’s text. Themeasure value will be rounded offto the precision specified.

This option is not available when atext expression is being used.

The default is to plot the negativesign for negative measure values.

The default is to flip the text asthe direction of the line changes.

A hatch definition can be drawn tothe left, right, or center of the line.Text is placed on the left side forthe center option.

The default is to draw line hatchesperpendicular to the line.

Label Settings dialog box

This dialog box is initiated by clicking the Label Settings button on the Hatch Definition view. The settings made on this dialog boxapply only to the currently selected hatch definition.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 91

DisplayinghatchesHatches are line or markersymbols displayed on top offeatures at an interval specifiedin route measure units. Hatchesallow you to make maps that aresuitable for almost any applica-tion that uses measured linearfeatures.

Layers based on linear featureswith measures always have atleast one hatch class associatedwith them. Initially, the defaulthatch class contains one hatchdefinition. Additional hatchdefinitions can be added to thishatch class. Each hatchdefinition has its own set ofproperties. These include themultiple of the hatch interval atwhich the hatches in the hatchdefinition will be placed, theline or marker symbol of thehatches, and whether the hatcheswill be labeled. The use ofmultiple hatch definitionsallows you to design complexhatching schemes.

Because hatch definitions mightshare many of the same proper-ties, it is possible to copy theproperties of a hatch definitionand change only the propertiesthat are different.

Any number of hatch classescan be associated with a layer. �

Hatching features in alayer

1. Right-click the layer in thetable of contents that youwant to hatch and clickProperties.

2. Click the Hatches tab.

3. Check Hatch features in thislayer.

4. Type an appropriate hatchinterval.

5. Click Hatch Def(1).

The Hatch Definition viewbecomes active.

6. Type an appropriate linelength. �

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92 LINEAR REFERENCING IN ARCGIS

Each hatch class can contain anynumber of hatch definitions. Onereason to create multiple hatchclasses is to hatch some featuresone way and other featuresanother way. To do this, youwould associate a SQL querywith your hatch classes. Anotherreason to have multiple classes isto have hatches appear differ-ently at different scales. To dothis, you would specify a scalerange with your hatch classes.

In situations when you needhatches at the end of features,you need to add an end hatchdefinition to the hatch class.

To appear on a map, hatchesmust be turned on via a checkbox. Note that it is possible toturn each individual class on oroff as well.

To save time, it is possible toimport hatches from anotherlayer. These layers may be in themap or may have been stored ondisk as a layer file (.lyr). Notethat if any of the hatch propertiesin the layer you are trying toimport from are based on a field(e.g., the hatch interval), thenthat field must exist in the layeryou are trying to import to.

Another time-saving method isthe use of hatch styles. For moreinformation on hatch styles, see‘Hatch styles’ in this chapter. �

7. Right-click the hatch classand click Add HatchDefinition.

The Hatch Definition viewbecomes active.

8. Type an appropriate multipleof the hatch interval.

9. Type an appropriate linelength.

10. Check Label thesehatches. �

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DISPLAYING AND QUERYING ROUTES AND EVENTS 93

Tip

Stopping the drawingprocessIf you selected a hatch intervalthat is too small, too many hatcheswill be drawn to the screen. Thedrawing process can be stopped bypressing the Esc key.

Tip

Hatches do not appear onthe mapIf hatches do not appear after youhave set up your hatch classes andhatch definitions, make sure that(1) the Hatch features in this layerbox is checked, (2) the box besideeach hatch class in the tree ischecked, (3) the specified hatchinterval is appropriate for thedata, and (4) all hatch definitionsthat use a line symbol have anappropriate line length specified.

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11. Right-click the hatch classand click Add End HatchDefinition.

The End Hatch Definitionview becomes active.

12. Type an appropriate endhatch tolerance if necessary.

13. Type an appropriate linelength.

14. Check Label these hatches.

15. Click OK.

Hatches do not respect theArcMap overposting environ-ment. As such, hatches and theirlabels can overlap one another.To avoid this, specifying adifferent hatch interval oftenalleviates the problem. In somesituations, however, it is desir-able to convert hatches tographics so they can be movedon the map.

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94 LINEAR REFERENCING IN ARCGIS

Importing hatches fromanother layer

1. Right-click the layer in thetable of contents that youwant to hatch and clickProperties.

2. Click the Hatches tab.

3. Click Import.

4. Click the Layer dropdownarrow and click the layer youwant to import hatches from.

Alternately, click the Browsebutton and navigate to thelayer file (.lyr) that you wantto import hatches from.

5. Click OK.

6. Click OK.

Tip

Making hatches and theirlabels bigger when youzoom inAs you zoom in and out on yourmap, the sizes of the hatches andtheir labels do not change. If youwant the hatches and text to scalewith the map, set a reference scale.Right-click the data frame andclick Set Reference Scale.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 95

Copying a hatchdefinition’s properties

1. Right-click the hatchdefinition that you want todefine the properties for andclick Copy Properties From.

2. Click the hatch definitiondropdown arrow and click thehatch definition whoseproperties you want to copy.

3. Click OK.

Tip

Removing hatch classesand hatch definitionsThe currently selected hatch classor hatch definition can be removedby right-clicking and clickingRemove or by pressing the Deletekey.

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96 LINEAR REFERENCING IN ARCGIS

Adding the ConvertHatches to Graphicscommand

1. Click Customize from theArcMap Tools menu.

2. Click the Toolbars tab.

3. Check Context Menus in theToolbars list.

The Context Menus toolbarappears.��

Tip

Why convert hatches tographics?You can convert hatches tographics so they can be moved,resized, and edited on the map.This option is useful for carto-graphic purposes.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 97

See Also

For more information on addingcommands to a toolbar or menu,see Using ArcMap.

�4. Click the Context Menusdropdown list and clickFeature Layer Context Menu.

5. Click the Commands tab.

6. Click Linear Referencing inthe Categories list.

7. Click the Save in dropdownarrow and click where youwant your customizationsaved.

8. Drag the Convert Hatches ToGraphics command to theFeature Layer Context Menu.

9. Click Close.

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98 LINEAR REFERENCING IN ARCGIS

See Also

For more information on graphicsor creating and editing annotationtargets, see Using ArcMap.

Converting hatches tographics

1. Right-click the layer in thetable of contents whosehatches you want to convertto graphics and click ConvertHatches To Graphics.

2. Click the features for whichyou want to create graphics.

3. Uncheck any hatch classesyou do not want converted tographics if appropriate.

4. Click the Target annotationgroup dropdown arrow andclick the annotation targetwhere you want to add thegraphics.

Alternately, type the name ofa new target annotationgroup.

5. Click OK.Tip

Drawing only convertedgraphicsIf you choose to only draw theconverted graphics, each hatchclass that was converted will beunchecked on the Hatches tab onthe Layer Properties dialog box.

Tip

Where should you savegraphics?If you want to display the graphicsonly in a particular map, storethem in the map. If you want to usethem in other maps, store them inan annotation feature class in ageodatabase.

Tip

Why does my targetannotation group notappear?If your desired target is ageodatabase annotation featureclass, you must first start an editsession. Then, you must set theArcMap active annotation target tobe that feature class.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 99

Manipulating thetext on hatchesEvery hatch definition may ormay not be labeled. Whenlabeled, you have control overthings such as the text symbolthat is used and whether or notthe text will automatically beflipped as the direction of theroute changes.

By default, the text associatedwith a hatch is the route measureat the hatch location. This textcan be supplemented with aprefix and/or suffix value.

For more advanced needs, youcan programmatically generate ahatch’s text by writing a script inMicrosoft® VBScript™ orJavaScript™. Your script caninclude any valid statementsthose programming languagessupport.

When writing a script, you accessthe route measure for each hatchusing the esri__measure constantvalue.

The script used in the followingexample tells the hatchingalgorithm not to label a hatch ifits measure value is within0.1 measure units of the valuestored in a field named MMAX.This method can be used insteadof an end hatch tolerance, whichtells the hatch algorithm not todraw either the hatch or its label.

Generating the text onhatches using a script

1. Right-click the layer in thetable of contents that youwant to hatch and clickProperties.

2. Click the Hatches tab.

3. Follow Steps 3 through 14 of‘Hatching features in a layer’if necessary.

4. Click the hatch definition ofyour choice.

5. Make sure the Label thesehatches check box ischecked.

6. Click Label Settings.

7. Click Build a text expression.

8. Click Expression.��

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100 LINEAR REFERENCING IN ARCGIS

See Also

For more information on VBScriptand/or JavaScript, click the Helpbutton on the Hatch Text Expres-sion dialog box.

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9. Check Advanced.

10. Type a VBScript orJavaScript expression.

ArcMap automaticallycreates a FindLabel functionin your code. FindLabelshould evaluate to a string.

11. Click Verify to make surethere are no syntax errors.

12. Click OK.

13. Click OK.

14. Click OK.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 101

Hatch stylesA hatch style stores the symbolsand the settings of the hatchdefinitions that make up a hatchclass. Hatch styles help youmaintain standards for displayingyour hatches on multiple mapswith multiple data sources.

When setting up hatch styles, it isimportant to note that some ofthe properties available whensetting up a hatch class are notavailable when setting up a hatchstyle. These are the propertiesthat are based on attributes, suchas class level offsets, startmeasures, and finish measures.

Like any other style in ArcMap,hatch styles are stored in a stylefile (.style). Unlike other styles,however, there are no industry-standard hatch styles that comewith ArcMap. It is up to you tocreate your own hatch styles.

Whether you are creating a newhatch style from scratch oraltering the properties of anexisting one, you use the StyleManager dialog box to work withhatch styles.

Creating a new hatchstyle in the StyleManager

1. Point to Styles from theArcMap Tools menu and clickStyle Manager.

2. Click the Hatches folder inthe style tree in the ESRIstyle file (.style) in which youwant to create a new hatchstyle.

3. Right-click in the open spacein the Style contents window,point to New, and click Hatch.

4. Set the style’s properties onthe Hatch Style propertiesdialog box and click OK.

5. Name the new hatch style.

See Also

For more information on styles,see Using ArcMap.

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102 LINEAR REFERENCING IN ARCGIS

Saving a hatch class as ahatch style

1. Click the hatch class that youwant to save as a hatch style.

2. Click Hatch Styles.

3. Click Save.

4. Type the name of the newhatch style.

5. Click OK.

6. Click OK.

7. Click Apply.

Tip

Accessing the Hatch Styledialog boxYou can also access the HatchStyle dialog box by right-clicking ahatch class in the hatch tree andselecting Hatch Styles.

Tip

Where are my hatch stylessaved?When you save a hatch class as astyle, it is saved to your ownpersonal style, which is locatedunder the Windows install location(e.g., C:\Documents andSettings\<user>\ApplicationData\ESRI\ArcMap). You can usethe Style Manager to move it to adifferent style file.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 103

Applying a hatch style toa hatch class

1. Click the hatch class to whichyou want to apply a hatchstyle.

2. Click Hatch Styles.

3. Click the hatch style you wantto use.

4. Click OK.

5. Click Apply.

Tip

Applying a hatch styleIf you apply a hatch style to ahatch class that already has somehatch definitions in addition to thedefault definition, they will beoverwritten by the hatchdefinitions in the hatch style.

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104 LINEAR REFERENCING IN ARCGIS

Route measureanomaliesThe ArcGIS system does notplace any constraints on routemeasures. Route measures canalways increase with respect to aroute’s digitized direction,always decrease with respect to aroute’s digitized direction, or besome combination of increasingand decreasing values. Lastly,route measures may be unknown(NaN).

Route measure anomalies areportions of routes where themeasures do not conform to thestandards your applicationexpects. With the ability todisplay what you deem to beroute measure anomalies inArcMap, you can ensure that themeasures on your routes conformto the needs of your application.Seeing where route measureanomalies occur can help youisolate routes that may need tohave their measures edited.

Displaying routemeasure anomalies

1. Right-click the route layer inthe table of contents that youwant to display route mea-sure anomalies for and clickProperties.

2. Click the Routes tab.

3. Click the route measureanomalies you want todisplay and change thesymbology as necessary.

Tip

Scale ranges and SQLqueriesUse a scale range and/or a SQLquery to control how routemeasure anomalies are displayed.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 105

Geographic data is represented on a map as a layer. Route eventsare no different. To display route events on a map, however, youmust first define the parameters of the relationship between thetable storing the events and the routes that the events reference.

Dynamic segmentation (DynSeg) is the process of computing themap location (shape) of events stored in an event table. Dynamicsegmentation is what allows multiple sets of attributes to beassociated with any portion of a linear feature.

The result of the dynamic segmentation process is a dynamicfeature class known as a route event source. A route event sourcecan serve as the data source of a feature layer in ArcMap.

Dynamic segmentation

0.2 11.12.00

1.31.92.1

31231

STOP

C3B2B2B2A1A1A1RID MILE

2

A1

B2C3D4

DynSeg

A1

B2

C3D4

0.2 11.12.00

1.31.92.1

31231

Point MPoint MPoint MPoint MPoint MPoint MPoint M

ShapeSTOP

C3B2B2B2A1A1A1RID MILE

2

Event table

Routes

Route event source Event layer

The result of the dynamic segmentation process can be displayed on amap as a layer.

For the most part, a dynamic feature layer behaves like any otherfeature layer. It is possible to decide whether or not to display it,the scale at which it should be visible, what features or subset offeatures to display, how to draw the features, whether to store itas a layer file (.lyr), whether to export it, and so on.

A route event source can be edited in ArcMap. It is important tonote, however, that it is possible to only edit the attributes. Theshapes of a route event source, however, cannot be editedbecause they are generated by the dynamic segmentation process.When you edit a route event, you are actually editing theunderlying event table. As such, there may be some editinglimitations imposed by the event table. For example, it is notpossible to directly edit the attributes of a route event sourcecreated from a delimited text file table since ArcMap does notallow text files to be edited directly.

Advanced dynamic segmentation options

Point events as multipoint features

When a point event is located along a route, a point feature iscreated. In some applications, however, route measures are notunique. For these applications, it might be desirable to have pointevents treated as multipoint features.

0.0

10.0

20.0

20.0

Point event at 15 as a point Point event at 15 as a multipoint

0.0

10.0

20.0

20.0

Point events can be located along routes as point features or multipointfeatures.

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106 LINEAR REFERENCING IN ARCGIS

90

180

270

075º

The dynamic segmentation process can calculate the angle of a route at apoint event’s location.

Event locating angles

When a point event is located along a route, it is often desirableto know the angle of the route where the event is placed. Forexample, you might need to rotate the marker symbol that is usedto display the event so it is oriented to the route and not the map.Further, you might need to rotate a point event’s label.

The dynamic segmentation process can calculate either thenormal (perpendicular) or tangent angle. Further, it is possible tocalculate the complement of these angles so you can, forexample, control the side of the route on which a rotated labelappears.

Event locating errors

The dynamic segmentation process creates a shape for each rowin the input route event table. In some cases, however, the shapeof the event feature might be empty. This happens when therewas some reason that the event could not be properly located. Inother cases, an event can only be partially located; this happensfor line events only.

The dynamic segmentation process can expose the locating error,if any, for each event in an event table as a field. This field isuseful when performing quality assurance tests on your eventtables.

Event offsets

In some applications, events with an offset are to be drawn to theright of the route. In other applications, events with an offset areto be drawn to the left. The dynamic segmentation process allowsyou to control which side of the route events with offsets isdrawn.

4.5 NO ERROR12.716.2

01.3

ROUTE MEASURE NOT FOUNDROUTE NOT FOUNDROUTE NOT FOUND

LOC_ERROR

B2B2A1A1A1RID MILE

NO ERROR

0.0

15.5

A1

5.5 11.013.116.2 3

NO ERRORPARTIAL MATCH FOR THE TO-MEASUREROUTE NOT FOUND

LOC_ERRORTMP

B2A1A1RID FMP

17.0

The dynamic segmentation process is aware of the locating status of eachevent. This information can be exposed as a field.

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DISPLAYING AND QUERYING ROUTES AND EVENTS 107

Adding routeeventsA route location describes aportion of a route or a singlelocation along a route. Whenroute locations are stored intables, they are known as routeevents. Route event tables aretypically organized around acommon theme. For example,an event table for highwaysmight include speed limits, yearof resurfacing, present condi-tion, and accidents.

There are two types of routeevents: point and line. Point �

Tip

Attribute indexesDynamic segmentation perfor-mance is improved with the use ofan attribute index on the routeidentifier field in both the eventtable and the route reference.

Tip

Displaying route eventsRight-click on an event table in theTable of Contents and clickDisplay Route Events.

Tip

Route identifier fieldThe Add Route Events dialog boxwill pay attention to a route layer’sroute identifier field.

1. Click Add Route Events fromthe ArcMap Tools menu.

2. Click the Route Referencedropdown arrow and click theroute reference layer.

Alternately, click the Browsebutton and navigate to theroute reference feature class.

3. Click the Route Identifierdropdown arrow and click theroute identifier field if neces-sary.

4. Click the Event Tabledropdown arrow and click theevent table.

Alternately, click the Browsebutton and navigate to theevent table.

5. Click the Route Identifierdropdown arrow and click theroute identifier.

6. Click the type of events theroute event table contains.

7. For point events, click theMeasure dropdown arrow andclick the Measure field.

For line events, click theFrom-Measure dropdownarrow and click the from-measure field. Click the To-Measure dropdown arrow andclick the to-measure field.

8. Optionally, click the Offsetdropdown arrow and click theoffset field.

9. Click Advanced Options. �

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108 LINEAR REFERENCING IN ARCGIS

Tip

Advanced optionsIt is possible to have the advanceddynamic segmentation optionsapplied to subsequent ArcMapsessions.

Tip

Layer filesYou save event layers as a layerfile (.lyr). The next time you bringthis file into ArcMap, the dynamicsegmentation process willautomatically be performed foryou.

events occur at precise locationsalong a route. Line eventsdescribe a portion of a route.

A route event table has at leasttwo fields: a route identifier andone or two measure locations.The route identifier indicates theroute the event is located along.The measure location is eitherone or two values describing thepositions on the route where theevent occurs.

The process of computing themap location of events stored inan event table is known asdynamic segmentation.

The result of the dynamicsegmentation process is a routeevent source, which can be usedby a layer in a map.

10. Click all of the advanceddynamic segmentations youwant applied to the routeevent source.

11. Click OK.

12. Click OK.

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IN THIS CHAPTER

109

ArcInfo and ArcEditor

Editing routes 6• Adding the Route Editing toolbar

• Creating routes from existinglines

• Calibrating routes with points

• Route measures

• Remeasuring routes

In addition to the display and query of routes and events, ArcMap is theapplication for creating and editing route features in your spatial database.ArcMap has tools for editing routes that are stored in shapefiles orgeodatabase feature classes.

When editing routes, it is important to remember that you are simplyediting linear features. If you already know how to edit linear features,you already know how to edit routes. The one thing that differentiates theediting of routes from other linear features is the presence of measurevalues stored with the feature’s vertices. Hence, the editing of routefeatures can be thought of as two distinct processes. The first is theediting of the route’s geometry. The second is the editing of the route’smeasures.

This chapter shows you how to edit routes and route measures in ArcMap.Route editing requires prior knowledge of editing linear features inArcMap. It is assumed that you already have a good understanding of howto edit linear features in ArcMap. For more information, see Editing inArcMap.

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Adding the RouteEditing toolbarBefore you edit your route datain ArcMap, you need to add theRoute Editing toolbar.

1. Point to Toolbars from theArcMap View menu and clickRoute Editing.

2. Click the toolbar’s title barand drag it to the ArcMapapplication window.

Tip

Adding the Route Editingtoolbar using theCustomize dialog boxFrom the ArcMap Tools menu,click Customize, click the Toolbarstab, then click Route Editing.

Tip

Adding the Route Editingtoolbar using the EditormenuFrom the Editor menu on theArcMap Editor toolbar, point toMore Editing Tools and clickRoute Editing.

Tip

Adding the Editor toolbarYou should also ensure that theEditor toolbar has been added. Todo this, click the Editor Toolbar

button on the ArcMapStandard toolbar.

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EDITING ROUTES 111

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Creating routesfrom existinglinesArcMap provides a variety oftools for creating linear features.Because a route is simply alinear feature with measures, ifyou are already familiar with thevarious techniques for creatinglinear features, you are alreadyfamiliar with some of thetechniques for creating routes.

The following pages outline thesteps for creating routes fromexisting line features. Thenumber of steps differs depend-ing on whether you want tocreate a simple or complexroute. A complex route loopsback on itself or branches.

When you create routes fromexisting lines, you must selectthe lines whose geometry youwant to copy to create the route.The selected features can befrom one or more of the linearfeature layers already in yourmap. Further, they can be fromany supported data format.

You can use any methodavailable to you to select thelinear features. For example, youcan use the Edit tool on theEditor toolbar, the SelectFeatures tool on the Toolstoolbar, Select by Attributes, andso on. �

Creating a simple route

1. Click the Task dropdownarrow and click Create NewFeature.

2. Click the Target layerdropdown arrow and click aroute layer.

3. Using any available method,select the linear feature orfeatures whose geometry youwant to copy to make theroute.

For example, click the Edittool on the Editor toolbar,move the mouse pointer overa feature, and click thefeature. Press the Shift keyand continue to click all thefeatures you want to use tocreate the route.

The selected features will behighlighted.

4. Click the Make Routebutton. �

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112 LINEAR REFERENCING IN ARCGIS

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TipCannot see the start pointon the map

If you cannot see the start point onthe map, it may be because you arenot zoomed out far enough to seeall of the endpoints of the selectedfeatures. Note that you can interactwith other ArcMap commands andtools (e.g., Pan, Zoom Out, Zoomto Selected Features) when theMake Route dialog box isdisplayed.

Once the linear features havebeen selected, you will use theMake Route dialog box to set theparameters for how your newroute will be created.

The first parameter you set is thestart point. This is where theroute measure values will begin.There are two ways to set thestart point. First, you can click apoint on the map. When youchoose this option, you will notethat as you drag your mousearound the map, the start pointautomatically snaps to one of theselected feature’s endpoints.Second, you can use a coordinatepriority of lower left, lower right,upper left, or upper right. Thesecoordinate priorities are deter-mined using the minimumbounding rectangle around theselected set of linear features.The endpoint from the selectedfeatures that is closest to thechosen coordinate priority will bewhere the measures start. �

5. Click the Start Point button.

6. Drag your mouse over theselected linear features andclick the map when the startpoint is where you want theroute measures to start.

7. Click how you want the routemeasure values to beobtained.

8. Click Make Route.

The newly created route isnow selected.

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The next parameter you setindicates how the measure valuesare to be obtained. When youchoose the geometric lengthoption, it is important to realizethat the geometric length of eachselected feature is determined inthe units of the target layer’scoordinate system and notnecessarily the feature’s nativecoordinate system. This is toaccount for the fact that within asingle data frame, features withdifferent coordinate systems canbe projected on the fly.

The measure field option is onlyenabled when all the selectedlinear features are from the samelayer. Measure values on the newroute will be accumulated usingthe values in this field.

Use the From/To option whenyou know the start and endmeasure values for the new route.All measure values between thestart and end will be interpolatedfor you.

The last parameter you setindicates whether or not youwant the measures to be continu-ous on disjointed routes. Notethat if you choose to havenoncontinuous measures, the gapdistance is calculated using theunits of the target layer’scoordinate system. This mightcause unexpected measurevalues, for example, when youuse a field that stores mileage �

Creating a complex(looping) route

1. Click the Task dropdownarrow and click Create NewFeature.

2. Click the Target layerdropdown arrow and click aroute layer.

3. Using any available method,select a simple chain oflinear features that do notform a loop.

For example, click the Edittool on the Editor toolbar,move the mouse pointer overa feature, and click thefeature. Press the Shift keyand continue to click all thefeatures you want to use tocreate the route.

The selected features will behighlighted.

4. Click the Make Routecommand on the RouteEditing toolbar. �

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114 LINEAR REFERENCING IN ARCGIS

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values to accumulate the measureand the target layer’s coordinatesystem units are meters. Note thatthis check box is not availablewhen the From/To option hasbeen chosen to set the measures.

Once the new route has beencreated in the target feature class,the selected set of input linearfeatures will become unselected,and the new route will becomeselected. This is so that you canset its attributes, such as the routeidentifier. For more informationon editing attributes, see Editingin ArcMap.

The process of creating acomplex route is similar to thatof creating a simple route. Theonly real difference is that youmust build a complex route inpieces. Once the pieces arecreated, they can be mergedtogether.

The work flow shown here forcreating a complex (looping)route is not the only one. Withyour knowledge of editing in �

5. Click the Start Point button.

6. Drag your mouse over theselected linear features andclick the map when the startpoint is where you want theroute measures to start.

7. Click how you want the routemeasure values to beobtained.

8. Click Make Route.

The newly created route isnow selected.

9. Using any available method,select a simple chain oflinear features that form thesecond half of the loop.

10. Click the Make Route tool onthe Route Editing toolbar. �

TipCoordinates or measuresout of bounds

If you get the Coordinates ormeasures out of bounds messagewhen creating a route, it isbecause the measure values thatare being applied to the new routedo not fit in the m domain. Formore information, see ‘Route data’in Chapter 4.

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ArcMap, you may choose a workflow that is more appropriate foryour organization.

Take note of the fact that in thecomplex route example shownhere, care has been taken to setthe measures appropriately foreach of the two halves of theroute that is eventually mergedtogether. If this is not possible inyour situation, you can stillmerge the pieces together. Thenat a later time, the measurevalues can be reset. For moreinformation, see ‘Remeasuringroutes’ in this chapter.

11. Click the Start Point button.

12. Drag your mouse over theselected linear features andclick the map when the startpoint is where you want theroute measures to start.

13. Click how you want the routemeasure values to beobtained.

14. Click Make Route.

The newly created route isnow selected.

15. Using any available method,select the two routes that willform the loop. �

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ArcInfo and ArcEditor

16. Click the Editor menu andclick Merge.

17. Click OK.

Tip

Preserving overlappingsegmentsThe Preserve overlappingsegments check box only appearswhen you are merging two routes.Make sure this box is checked (thedefault) when you are creating alooping route.

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Calibratingroutes withpointsIt is important to have accuratemeasure values along routes,especially when the measuresare used to tie in large amountsof event data.

It is possible to adjust routemeasures to correspond withknown measure locations with aprocedure called calibration.Calibration adjusts routemeasures using points. A routecan be successfully calibratedwith two or more points.

Once you have selected theroute that you want to calibrate,you must digitize the points touse for calibration. To digitizethe points, you use the Sketchtool. Optionally, you can set thesnapping environment. Forexample, you might want tosnap to points that are stored inanother feature class. Becauseone route is calibrated at a time,there is no point-to-route cutofftolerance specified. All digitizedpoints will be assumed to fall ontop of the selected route. �

1. Click the Task dropdownarrow and click CalibrateRoute Feature.

2. Click the Edit tool, move themouse pointer over a routefeature, and click the feature.

3. Click the Calibrate Route toolon the Route Editing toolbar.

The Calibrate Route dialogbox will appear.

4. Click the Sketch tool.

5. Click the map at eachlocation you want a calibra-tion point.

You will see the CalibrateRoute dialog box’s point listbeing populated as you clickthe points. �

Tip

UndoIf you digitize a point you do not

like, click the Undo buttonon the ArcMap Standard toolbar.

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6. Type the new measure valuefor each clicked point.

7. Click the calibration optionsyou would like.

8. Click Calibrate Route.

Once all the calibration pointshave been digitized, you mustthen type the new measure valuefor each point.

Either whole or partial routescan be calibrated. You canchoose to interpolate betweenthe calibration points, extrapo-late before the calibrationpoints, extrapolate after thecalibration points, or use anycombination of these methods.

In order for the measure valueon a vertex to be interpolated orextrapolated, a calibration ratiois needed. There are two waysthis ratio can be determined. Thefirst method uses the shortestpath distance between the inputpoints. The second method usesthe existing measure distancebetween the input points.

When calibrating disjointedroutes, you may choose toignore the distance of the spatialgap between the parts. If youchoose to ignore spatial gaps,route measures will be continu-ous. If you want the spatial gapincorporated in the measures,the gap distance is the straight-line distance between theendpoints of the parts.

Tip

Order is importantMake sure you digitize thecalibration points in either routeincreasing or decreasing order,rather than in some random order.

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Route measures

Editing existing routes

Whenever a route’s geometry is edited in ArcMap, its measurevalues are edited as well. Because of this, there are three rulesthat are followed whenever a route’s geometry is changed.

First, the measure value on newly added vertices is interpolatedwhen the new vertex falls between two vertices with knownmeasure values.

A new vertex will have its measure value interpolated only when it iscreated between two vertices that have known measure values.

0

1

2

3

0

1

2

31.5

0

NaN

2

3

0 2

3NaNNaN

Case A Case B

0

1

2

3

0

1

2

3

NaN

NaN

A new vertex will not have its measure value extrapolated when a route isextended.

0

5

15

20

32

1 0

Intersect7.5

12.5

2

1- or -

When geometries overlap, some editing commands must choose which ofthe input feature’s measures will be used for the output. In these cases,the measures from the feature that was selected first will be used. In thisintersect example, both possible results are shown.

40m

0 10 20 30 40

Set measures as the distance from the route’s origin.

Second, in cases where a route’s geometry has been extended,newly added vertices will not have their measure valueextrapolated.

Finally, certain editing commands, such as Merge, Union, andIntersect, take two or more input geometries and produce anoutput geometry. In some cases, these commands will encountersituations where the input geometries overlap. Consequently,these commands must choose which of the input feature’smeasures to use in the output. In such cases, the measure valuesfrom the feature that was selected first will be used.

Setting route measures

The following methods can be used to set a route’s measurevalues. It is possible to apply all of these methods to whole orpartial routes.

Set As Distance—Set the route’s measure values to be thecumulative length from the origin of the geometry. Hence, routemeasures will increase with the digitized direction of the route.

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5 15 25 35 45

0 10 20 30 40

Offset route measures by 5.

0 10 20 30 40

0 NaN NaN 30 NaN

Interpolate or extrapolate unknown measure values.

NaN

0 10 20 30 40

NaN NaN NaN NaN

Set all route measures to NaN.

0 10 20 30 40

0 10 20 30 40

Set a route’s digitized direction to match the direction of the measures.

Set From/To—Set the route’s measures using known start andend values. All measure values between the start and end will beinterpolated.

In some applications, the ratio between a route’s length and itsmeasures is not constant. When the Set From/To method isapplied to a route, it is possible to preserve the measure schemathat exists. That is, this method can assign measure values basedon the original measure value.

Sometimes a constant change needs to be applied to a route’smeasures. This is the case whenever measures need to be rescaledor converted into different units or simply incremented by somevalue. You can meet these needs by using the next two methods.

Apply Factor—Multiply a route’s measures by a factor.

Set the start measure to be 0 and the end measure to be 100. All measurevalues in between are interpolated.

0 25 50 75 100

0 2 4.5 7 10

0 20 45 70 100

Do not preserve existing measureschema

Preserve existing measure schema

0 25 50 75 100

0 2.5 5.0 7.5 10.0

Multiply route measures by a factor of 10.

Offset—Add a value to a route’s measures.

Calculate NaN—Interpolate or extrapolate all route measuresthat are unknown (NaN).

Drop Measures—Set all route measures to NaN.

Set Direction As M—There is no requirement that a route’smeasures increase with the digitized direction. This method willflip a route’s geometry to match the direction in which themeasures are increasing.

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RemeasuringroutesRoute measures need to beedited, for example, when moreaccurate information has beenobtained or when the geometryof the route has been altered insome way.

Route measures are edited viaan edit sketch. When editingroute measures, the edit sketchis simply a shape that representsa copy of the route’s geometry.Once you have made thenecessary changes to the routemeasures, you finish the editsketch. Finishing the sketchwrites the sketch geometry toroute. �

Setting measures asdistance

1. Click the Task dropdownarrow and click ModifyFeature.

2. Click the Edit tool, move themouse pointer over the routefeature you want toremeasure, and click thefeature.

A copy of the selected route’sgeometry is written to the editsketch.

3. Right-click on the edit sketch,point to Route MeasureEditing, and click Set AsDistance.

4. Type the starting measurevalue and press Enter.

At this point, the changes tothe measures have beenapplied to the sketch only. Tofinish the sketch, press F2 orsimply unselect the routefeature.

Tip

Double-clicking to modify afeatureWhen the Edit tool is selected, youcan double-click a feature whenyou want to modify it. The edit taskwill automatically change toModify Feature.

Tip

Edit Sketch PropertiesBecause route measures are set onan edit sketch, open the EditSketch Properties dialog boxif you want to see the changes asthey happen.

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Setting from/to measures

1. Click the Task dropdownarrow and click ModifyFeature.

2. Click the Edit tool, move themouse pointer over the routefeature you want toremeasure, and click thefeature.

A copy of the selected route’sgeometry is written to the editsketch.

3. Right-click on the edit sketch,point to Route MeasureEditing, and click Set From/To.

4. Type the from and to mea-sure values, click whetheryou want to preserve theexisting measure schema,and press Enter.

At this point, the changes tothe measures have beenapplied to the sketch only. Tofinish the sketch, press F2 orsimply unselect the routefeature.

Realigning a route is the act ofdefining a new course for a route.Once a route is realigned, youmay need some portions of theroute measures to remainunchanged, while other portionsneed to be updated. Because ofthis need, it is possible toremeasure whole routes orportions of routes. �

Tip

Using the Route MeasureEditing options multipletimesThere are many situations in whichyou may need to use the RouteMeasure Editing options more thanonce to achieve the desired result.For example, you may want theroute measures on a new route tobe stored in miles. The routefeature class, however, has beendigitized in feet. An easy solutionto this is to first use the Set AsDistance option to set the mea-sures in feet. Then the ApplyFactor option could be used toconvert from feet to miles (thefactor would be 0.00018939394).

TipCoordinates or measuresout of bounds

If you get the Coordinates ormeasures out of bounds messagewhen remeasuring a route, it isbecause the measure values thatare being applied to the route donot fit in the m domain.

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EDITING ROUTES 123

ArcInfo and ArcEditor

Remeasuring a portion ofa route

1. Click the Task dropdownarrow and click ModifyPortion of a Line.

2. Click the Edit tool, move themouse pointer over the routefeature you want toremeasure, and click thefeature.

3. Click the Define Line Portiontool.

4. Click a point along theselected route to startdefining the portion.

5. Click a second point alongthe selected route to finishdefining the portion.

An edit sketch is created.

6. Right-click on the edit sketch,point to Route MeasureEditing, and click the optionyou want to use to remeasurethe portion.

When you are defining a portionof a route to be remeasured, youare actually creating a sketchwhose geometry represents justthe defined portion. Once thesketch has been created, you usethe Route Measure Editingsketch menu—just like youwould if you were remeasuringthe entire route.

Tip

Number of decimalsThe number of decimals displayedwhen defining the subportion of aroute corresponds to the number ofdecimals setting on the Generaltab of the Editing Options dialogbox.

Tip

Map tip textWhen defining a portion of a routeto be remeasured, the text of themap tip corresponds to themeasure value at that point alongthe selected route.

Tip

Context menuWhen you are defininga portion of a route,you can right-click onthe map to display acontext menu. Theoptions on this menuallow you to quicklymove to any pointalong the route.

� �

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IN THIS CHAPTER

125

Creating and editing event data 7• Creating and editing event data

• Creating event tables inArcCatalog

• Overlaying events

• Aggregating events

• Transforming event measures

• Locating points along routes

• Locating polygons along routes

• Editing event tables in ArcMap

An event table is just like any other table in ArcGIS Desktop; it is adatabase component that contains a series of rows and columns. In an eventtable, each row describes a location along a route, and each columnrepresents a particular attribute about the route location. Event tables arestored in any supported format—for example, INFO, Microsoft Access,dBASE, Oracle®, SQL Server™, delimited text files, and those databasesaccessed via OLE DB providers.

In this chapter, you will learn how to create and edit event data and tables.However, before you start creating and editing event data, note that manyorganizations already maintain large event databases. Quite often, thesedatabases can be accessed and their tables can be used as events withoutany modification. Any table that contains route identifier and route measurefields—the route location fields—can be used as an event table.

Event tables are generally created in ArcCatalog. They can also be createdin the ArcMap Route Events GeoProcessing Wizard. Once created,ArcMap makes it easy to view and update the attributes of the events inyour database.

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126 LINEAR REFERENCING IN ARCGIS

Creating and editing event data

Creating event data

In order to be used as an event table, a table must contain routelocation fields, which are used to find the location of the eventsalong routes.

Event tables can be created in ArcCatalog, where there are toolsfor creating geodatabase, dBASE, and INFO tables.

Event data can be stored in any supported table. Shown here aregeodatabase, text file, INFO, and dBASE tables.

geodatabase

text file

INFO

dBASE

There are some additional techniques that automate the task ofevent table creation:

• Creating point events by locating point features along routes

• Creating line events by locating polygon features alongroutes

• Overlaying existing event data to create new line or pointevents

• Aggregating existing event data using concatenate anddissolve operations

• Transforming route measures from one route reference toanother

Overlaying events

In ArcMap, geographic data is represented on a map as a layer.When event data has been added to a map in the form of a layer(see ‘Adding route events’ in Chapter 5), it can be queriedaccording to feature locations and attributes to solve problems.Further, new spatial relationships can be discovered by askingquestions such as Where is...?, Where is the closest...?, andWhat intersects...? For more information on how to find answersto these types of questions, see Using ArcMap.

Overlaying events is another way to create new event data. Thisprocess combines two input event tables to create a single outputevent table. The new table can be used to analyze event data inways not possible using traditional spatial analysis techniques.

The new event table can contain either the intersection or theunion of the input events. The union of the input events splits alllinear events at their intersections and writes them to the newevent table. The intersection of the input event tables writes onlyoverlapping events to the output event table.

Line-on-line, line-on-point (same as point-on-line), and evenpoint-on-point event overlays can be performed.

Line-on-line overlay

A line-on-line overlay involves the overlay of two line eventtables to produce a single line event table.

ArcInfo

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CREATING AND EDITING EVENT DATA 127

0.0 10.0 20.0 30.0 40.0 50.0Line-on-line overlay

Input table

Overlay table

Union

Intersect

AB

AABB

BA

A/AAB/AA

A/BBA

A/AAB/AA

A/BB

B/BB

Line-on-point overlay

Input table

Overlay table

Union

Intersect

0.0 10.0 20.0 30.0 40.0 50.0A

B

AA BB

BB

AC

C

C

CC

B/AA A/BB A/CCB/BB C/CC

B/AAA/BBB/BB

A/CCC/CC

The example below shows the union of a line event table thatstores pavement information and another line event table thatstores pavement resurfacing dates. The result can be used, forexample, to find the characteristics of the oldest paved sections.

Line-on-point overlay

A line-on-point overlay involves the overlay of a line event tableand a point event table. The process produces a single pointevent table.

The example below shows the intersection of a point event tablecontaining accident locations and a line event table containingpavement information. The result can be used, for example, toanalyze pavement characteristics where accidents occurred.

23.5 44.244.284.7167.4182.8

167.4182.8209.5

5030809545

CRACKTMP

101101101101101RID FMP

84.7

45

3.2 21.123.544.284.721.195.5

167.4

84.795.523.5167.4182.8

05030800

8095

2/5/859/3/879/3/879/3/879/3/874/28/614/28/61

RESURFCRACKTMP

101101101101101101101RID FMP

44.2

101 182.8 190 4/28/61

23.5 44.244.284.7

167.4167.4182.8

2/5/859/3/87

4/28/611/21/74

RESURFTMP

101101101101RID FMP

84.7

Unioning two event tables can help expose spatial relationships notevident before the overlay. Here, two line event tables are unioned. Theoutput event table contains all of the input events, which have been splitwhere they intersected.

23.5 44.244.284.7167.4182.8

167.4182.8209.5

5030809545

CRACKTMP

101101101101101RID FMP

84.725.9 295.6

172.3180.3

13

0101

ALCINJ

101101101101RID MILE

1

25.9 295.6172.3180.3

13

0101

50809595

CRACKALCINJ

101101101101RID MILE

1

Intersecting two event tables can help expose spatial relationships notevident before the overlay. Here, a line and a point event table have beenintersected.

ArcInfo

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128 LINEAR REFERENCING IN ARCGIS

Aggregating event data

You aggregate existing event data using concatenate anddissolve operations. These operations are designed to helpmaintain the integrity of large event tables.

Both the concatenate and dissolve operations combine eventrecords in tables where there are events on the same route andthey have the same value for specified fields. The result is writtento a new event table. One difference between the two operationsis that concatenate will only combine events in situations wherethe to-measure of one event matches the from-measure of the nextevent. Dissolve will combine events when there is measureoverlap. Another difference is that the dissolve operation isavailable for both line and point event tables, while theconcatenate operation is available only on line event tables.

You can use concatenate or dissolve to remove redundantinformation from an event table. For example, if one linear event ina pavement event table has an attribute—concrete—from 0 to100, and the following event record has an attribute—concrete—from 100 to 125, the two events will be merged into a single eventfrom 0 to 125. Getting rid of redundant event information makes allsubsequent operations on the events more efficient.

Another use for concatenate or dissolve is to break up eventtables having more than one descriptive attribute into separatetables. For example, if a pavement event table has fields LANESand MATERIAL, the event table can be subdivided into twotables: one having the attribute LANES, and the other having theattribute MATERIAL. To do this, the dissolve or concatenateprocess would need to be run twice.

Dissolve

Concatenate

Input table

0.0 10.0 20.0 30.0 40.0 50.0

Concatenating and dissolving events

AA

AA

A

A

AA

A

Concatenating and dissolving events combine adjacent records in linearevent tables if they are on the same route and have the same values forthe dissolve field or fields.

1 01111

125175205

100125175205215

concreteconcreteasphaltasphalt

concrete

MATERIALTMPFMPRID

100 1 011 205

125205215

concreteasphalt

concrete

MATERIALTMPFMPRID

125

Concatenating or dissolving events can be used to remove redundantinformation from event tables.

0 15150

12516535

125165210155

224242

concreteasphaltasphalt

concreteconcreteasphalt

MATERIALLANESTMP

322211

RID FMP

90

0 900

12516535

165210155

24242

LANESTMP

32221

RID FMP

125

0 15150

12535

125210155

concreteasphaltasphalt

concreteasphalt

MATERIALTMP

32211

RID FMP

90

Concatenating or dissolving events can also be used to break up eventtables with multiple descriptive attributes.

ArcInfo

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CREATING AND EDITING EVENT DATA 129

Transforming event measures

In certain circumstances, it may become necessary to update themeasure values in an event table. For example:

• Using an event table to reference multiple route references,each of which has its own unit of measure

• Keeping measures up to date when a route is recalibrated orrealigned

Use with multiple route references

In many agencies, event data is collected against multiple routereference systems. For example, a DOT might use both a referencemarker system and a milepoint system. Some event data, such asaccident locations and maintenance activities, is recorded usingthe reference marker system, while other event data, such aspavement condition or capital improvement projects, is recordedusing the milepoint system of measurement.

Every year, a DOT manager is required to determine whichsections of highway need to be resurfaced. Using a pavementevent table, a manager could determine which segments ofpavement have fallen into ill repair. The manager does not,however, want to resurface highways with certain types ofaccident histories without first performing a safetyanalysis. The reason for this is that speeds may increase on thenew pavement, which could increase the accident rate evenfurther.

In order to make a well-informed decision, it will be necessary tocombine and analyze the event data that has been collectedagainst the different route references. The pavement scores arebased on milepoint values, while the accident data is based onreference marker system. To combine the event data, thepavement events must be transformed to the reference marker

system, or the accident events must be transformed to themilepoint system.

In most cases, you will use the ArcMap Route EventsGeoProcessing Wizard to transform events from one routereference to another. This wizard calculates the x,y coordinatelocation of each event in an input route reference and matchesthis to the corresponding measure values in a second routereference. The structure of the routes need not be the same. Anew event table is written out with the events encoded in adifferent system of measures.

In cases in which route structure is identical and the difference inmeasures between two reference systems is constant, a simplemathematical equation can be used in lieu of the Route EventsGeoProcessing Wizard to transform event measures. For example,if one route reference has its measures in miles and the other hasits measures in feet, then all that needs to be done is to multiplythe miles by 5,280 in the field calculator to obtain feet.

Keeping event measures up to date

Measure locations tie an event to a particular location along aroute. When the measures of a route are altered, the events willno longer be mapped to the same position along their routes.

0.2 0.40.41.6 2.4

fairgoodpoor

ConditionTMP

MP1MP1MP1RID FMP

1.6

102.2 102.4102.4103.6 104.4

fairgoodpoor

ConditionTMP

RM9RM9RM9RID FMP

103.6

Milepoint

0

2.5

Reference Marker

102

105

It is necessary to transform events to analyze events recorded usingone route reference with events recorded using another routereference.

ArcInfo

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130 LINEAR REFERENCING IN ARCGIS

In some cases, this is the desired result. For example, if themeasures along a stream need calibration to match up to knownmileages at gauging stations, and the location of fish habitatevent data was collected using the gauging stations, thennothing needs to be done to the event data when the routemeasures are altered.

In other cases, the location of the events when they are mappedmust be maintained. For example, if a highway is realigned, themeasure of events describing the location of road signs must beupdated to maintain their original positions.

If changes in route measures are linear along the length of aroute, an equation can be applied to the event measures. Forexample, if a route’s measures are multiplied by a factor of 1,000 toconvert from kilometers to meters, all event measures can also bemultiplied by 1,000.

If changes in route measures are nonlinear, such as what happensduring a realignment procedure, then the ArcMap Route EventsGeoProcessing Wizard can be used to recalculate the measures inan event table to maintain the real-world locations.

Locating point features along routes

When you locate point features along routes, you aredetermining the route and measure information of where yourpoint data intersects your route data.

Locating point features along routes is useful, for example, whenyou need to locate:

• Signs along highways

• Wells or gauging stations along river reaches

• Stops along bus routes

• Manholes along city streets

• Valves along pipes

50% original length

50% edited length

Realigning a route causes measure values to change. Events located onthis route will no longer be in the same position.

A101 0A101A101A101A101A101

14.723.933.238.1

Measure

654321

Point_ID Route_ID

4.9

0 40

A101

Locating points along routes creates a new point event table containingthe route identifier and measure information of where points intersectroutes.

ArcInfo

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CREATING AND EDITING EVENT DATA 131

Locating polygon features along routes

Locating polygon features along routes computes the route andmeasure information at the geometric intersection of polygon dataand route data. Once polygon data has been located alongroutes, the resulting event table can be used, for example, tocalculate the length of route that traveled through each polygon.

Locating polygon features along routes is useful, for example,when you need to locate:

• Soils, spillways, areas of inundation, or hazard zones alongriver reaches

• Wetlands, hazard zones, or town boundaries along highways

Editing event data

Event tables are only as good as the information they contain.Over time, you will need to modify event data to keep it accurateand up to date. ArcMap lets you edit event data. You can editany of the attribute values in an event table as well as add anddelete event records. You can also use the field calculator tochange the attribute value of a field for several events at once.

Locating polygon data along routes computes the geometric intersectionof the route and polygon data.

A101 5A101A101 24

162438

To_MFrom_M

321

Poly_ID Route_ID

16

0 40

A101

ArcInfo

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132 LINEAR REFERENCING IN ARCGIS

Creating eventtables inArcCatalogYou can create geodatabase,dBASE, and INFO event tablesin ArcCatalog with easy-to-usetable designers.

For a table to be considered anevent table, it must contain theappropriate route locationfields. For point event tables,the required fields are a routeidentifier field and a measurefield. For line events, therequired fields are a routeidentifier field plus both a from-and a to-measure field. All otherfields define each point or lineevent’s attribute information. �

Creating a table in ageodatabase

1. Right-click the database inthe Catalog tree in which youwant to create a new table,point to New, then clickTable.

2. Type a name for the table. Tocreate an alias for this table,type the alias.

3. Click Next. �

See Also

For more information aboutcreating a table in a geodatabase,see Building a Geodatabase.

Tip

Route location fieldsThe route identifier field can beany numeric or character datatype. You should consider creatingan attribute index on the routeidentifier field; it will help improvedynamic segmentation perfor-mance. The measure field or fieldsmust be a numeric data type.

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CREATING AND EDITING EVENT DATA 133

See Also

For more information aboutconfiguration keywords withArcSDE, see the ArcSDE Configu-ration and Tuning Guide for<DBMS> PDF file.

Tip

OBJECTID field in ageodatabase tableThe OBJECTID field in ageodatabase table uniquelyidentifies each object stored in thetable. It cannot be deleted.

When defining an event table’sname and fields, be aware thateach database has its own rulesdefining what names andcharacters are permitted. Referto your database’s documenta-tion for a list of these rules.

For dBASE tables, the processof defining the attributes isseparate from creating the tableitself. After creating the table,you need to right-click it in theCatalog tree and click Propertiesto define the attributes.Because they must contain atleast one field, the text fieldName1 is added. Add theappropriate fields to the dBASEtable, then delete the defaultfield. In a dBASE table, a fieldname must be 10 characters orless; additional characters willbe truncated. �

If your table does not useArcSDE, skip to step 6.

4. Click Use configurationkeyword and type thekeyword if you want to createa table using a customstorage keyword.

5. Click Next.

6. Click the next blank row inthe Field Name column andtype in a name to add a fieldto the table.

7. Click in the Data Typecolumn next to the new field’sname and click its data type.

8. Click the field next to Aliasand type the alias name forthis field to create an alias forthis field.

9. Click the field next to AllowNULL values and click No toprevent nulls from beingstored in this field.

10. Click the field next to DefaultValue and type the value toassociate a default valuewith this field.

11. Click the field next toDomain and click thedomain to associate adomain with this field.

12. Repeat steps 6 through 11until all the table’s fieldshave been defined.

13. Click Finish.

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134 LINEAR REFERENCING IN ARCGIS

Creating a dBASE table

1. Right-click the folder in theCatalog tree in which youwant to create the new table,point to New, then clickdBASE Table.

A new dBASE table appearsin the folder’s contents.

2. Type the name for the tableand press Enter.

3. To add a field to the table,right-click the table in theCatalog and click Properties.

4. Click the Fields tab.

5. Click the next blank row inthe Field Name column andtype in a name.

6. Click in the Data Typecolumn next to the newfield’s name and click its datatype.

7. Click in the Field Propertieslist and type the propertiesfor the new field.

8. Repeat Steps 5 through 7until all the table’s fieldshave been defined.

9. Click OK.See Also

For more information aboutcreating a dBASE table, see UsingArcCatalog.

Tip

OID field in a dBASE tableThe OID field in a dBASE table is avirtual field that is created byArcGIS when the table’s contentsare accessed. It is used to ensurethat each object in the table has atleast one unique value. It cannot bedeleted.

� �

An INFO table’s name must be32 characters or less, and theitem names must be 16 charac-ters or less. Items are definedusing standard ArcInfo datatypes. The input width is themaximum number of charactersor bytes used to store the item’svalues. For numeric items, thewidth must be large enough toaccommodate the decimal pointand negative sign. The displaywidth is the number of spacesused to display values inArcInfo Workstation; fordecimal values, the displaywidth should be one spacegreater than the input width toaccount for the decimal point.

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CREATING AND EDITING EVENT DATA 135

Creating an INFO table

1. Right-click the folder in theCatalog tree in which youwant to create the new table,point to New, then click INFOtable.

2. Type a name for the newtable.

3. Click the data type of the firstitem in the table.

4. Type the name for the newitem.

5. Change the column width,display width, and decimalplaces as necessary.

6. Click New item to addanother item to the table.Then repeat steps 3 through5 to define the new item’sproperties.

7. Repeat step 6 until all itemshave been added to thetable.

8. Click OK.

See Also

For more information aboutcreating an INFO table, see UsingArcCatalog.

Tip

Creating a new workspaceAll INFO files must reside withinan INFO workspace. To create anew workspace, right-click on thefolder where the workspace willreside in the Catalog tree, point toNew, then click ArcInfo Workspace.

ArcInfo and ArcEditor

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136 LINEAR REFERENCING IN ARCGIS

Overlaying eventsYou can use the ArcMap RouteEvents GeoProcessing Wizardto overlay event tables. Line-on-line, line-on-point, and evenpoint-on-point event overlayscan be performed.

The event overlay options areonly enabled when there aretwo or more event layers inyour map.

To overlay successfully, boththe event layers should bebased on the same routereference. Otherwise, you mayget erroneous results.

The output event table cancontain either the intersectionor the union of the inputevents. The union of the inputevents splits all linear events attheir intersections and writesthem to the new event table.The intersection of the inputevent tables writes onlyoverlapping events to theoutput event table.

If either of the input tablescontains point events, theoutput will always be a pointevent table.

The new event table can bewritten to the workspace ofyour choice. �

Overlaying events—Intersect

1. Click the Tools menu andclick Route EventsGeoProcessing Wizard.

2. Click Intersect two routeevent layers.

3. Click Next.

4. Click the input route eventlayer dropdown arrow andclick the input event layer.

5. Click the overlay route eventlayer dropdown arrow andclick the overlay event layer.

6. Click Next.

7. Click the Browse button andnavigate to a location to savethe output event table.

Alternatively, you can typethe name and location of theoutput event table.

8. Type the names of the outputroute location fields if youwant to change thesuggested defaults.

9. Check whether you wouldlike to include all the fieldsfrom the input event layers.

10. Check whether you wouldlike the output table addedto the map as an event layer,as a standalone table, or notat all.

11. Click Finish.

ArcInfo

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CREATING AND EDITING EVENT DATA 137

Overlaying events—Union

1. Click the Tools menu andclick Route EventsGeoProcessing Wizard.

2. Click Union two route eventlayers.

3. Click Next.

4. Click the input route eventlayer dropdown arrow andclick the input event layer.

5. Click the overlay route eventlayer dropdown arrow andclick the overlay event layer.

6. Click Next. �

Tip

Using the selectedfeaturesWhen you overlay events, you canchoose whether you want toprocess only the selected set offeatures.

By default, the output eventtable contains a route identifierfield, the measure fields, plus allof the input event attributes.You can choose to not write outthe event attributes. In thiscase, only the respective eventlayer’s OBJECTID field will bewritten to the output table. Thisfield can be used at a later timeto join or relate back to theoriginal event attributes.

When both inputs are lineevent tables, you can specifywhether you want to keep zerolength line events in the outputtable. These are events wherethe from- and to-measures areequal and are often created bythe overlay process.

You can choose to have theresulting table added to the mapas a feature layer, as astandalone table, or not at all.

ArcInfo

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138 LINEAR REFERENCING IN ARCGIS

Tip

Definition queriesWhen you overlay events, anydefinition queries set up on theinput event layers will be respected.

7. Click the Browse button andnavigate to a location to savethe output event table.

Alternatively, you can typethe name and location of theoutput event table.

8. Type the names of the outputroute location fields if youwant to change thesuggested defaults.

9. Check whether you wouldlike to include zero lengthline events in the output tableif you are overlaying two lineevent layers.

10. Check whether you wouldlike to include all the fieldsfrom the input event layers.

11. Check whether you wouldlike the output table addedto the map as an event layer,as a standalone table, or notat all.

12. Click Finish.

ArcInfo

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AggregatingeventsYou can use the ArcMap RouteEvents GeoProcessing Wizardto aggregate event data. Usethe Dissolve/Concatenate routeevents option to removeredundant information fromevent tables or to break upevent tables having more thanone descriptive attribute intoseparate tables. The result willbe written to a new event tablein the workspace of yourchoice. This option is onlyenabled when there is one ormore event layers in your map.

Select concatenate when youwant to only combine events insituations in which the to-measure of one event matchesthe from-measure of the nextevent. Select dissolve whenyou want to combine eventsthat have overlapping mea-sures.

You can dissolve or concat-enate on one or more fields.

You can choose to have theresulting table added to themap as a feature layer, as astandalone table, or not at all.

Dissolving andconcatenating routeevents

1. Click the Tools menu andclick Route EventsGeoProcessing Wizard.

2. Click Dissolve/Concatenateroute events.

3. Click Next.

4. Click the event layerdropdown arrow and clickthe event layer to be dis-solved/concatenated.

5. Click whether you would liketo dissolve or concatenatethe events.

Concatenate will be unavail-able if you selected a pointevent layer in Step 4.

6. Check the box to indicate theattribute or attributes onwhich to dissolve orconcatenate.

7. Click Next. �

ArcInfo

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Tip

Definition queriesWhen you aggregate events, anydefinition queries set up on theinput event layer will be respected.

Tip

Using the selectedfeaturesWhen you aggregate events, youcan choose whether you want toprocess only the selected set offeatures.

8. Click the Browse button andnavigate to a location to savethe output event table.

Alternatively, you can typethe name and location of theoutput event table.

9. Type the names of the outputroute location fields if youwant to change thesuggested defaults.

10. Click whether you would likethe output table added to themap as an event layer, as astandalone table, or not atall.

11. Click Finish.

ArcInfo

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Transformingevent measuresThere are two ways you cantransform event measures inArcMap. First, if the requiredtransformation is constant, youcan use the field calculator. Forexample, you can use the fieldcalculator to easily transformevent measures between feetand miles.

Second, you can use the RouteEvents GeoProcessing Wizard’sTransform events from oneroute reference to anotheroption. The wizard will write anew event table to theworkspace of your choice. Thisoption is only enabled whenthere are two or more eventlayers in your map.

To be transformed successfully,the input events must be withina specified tolerance of theroutes in the target route �

Transforming eventmeasures using the fieldcalculator

1. Click the Editor menu on theEditor toolbar and click StartEditing if you have notalready started an editsession.

2. Open the table you want tostart editing.

3. Select the records you wantto update. If you don’t selectany, calculations will beapplied to all records.

4. Right-click the field headingfor which you want to make acalculation and clickCalculate Values.

5. Use the Fields list andFunctions list to build acalculation expression. Youcan also edit the expressionin the text area below. Lastly,you can just type in a valueto set the field to.

6. Click OK.

Tip

Calculating fields outsidean edit sessionYou can calculate field valuesoutside of an edit session. Youcannot, however, undo yourchanges.

See Also

For more information on fieldcalculations, see Using ArcMap.

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Transforming eventsusing the Route EventsGeoProcessing Wizard

1. Click the Tools menu andclick Route EventsGeoProcessing Wizard.

2. Click Transform events fromone route reference toanother.

3. Click Next.

4. Click the event layerdropdown arrow and clickthe event layer to betransformed.

5. Click the Route Referencedropdown arrow and clickthe target route layer.

6. Click the Route Identifierdropdown arrow and clickthe route identifier.

The route identifier uniquelyidentifies each route.

7. Type the search tolerance,click the dropdown arrow,then click the appropriateunits.

The tolerance defines howfar an event can be from atarget route in order to betransformed.

8. Click Next. �

Tip

Route structureWhen transforming events, theinput route structure and targetroute structure need not be thesame.

Tip

Choosing a toleranceThe larger the tolerance you use,the more likely an event will betransformed to the incorrect routein the target route reference. Useas small a tolerance as possible toachieve the best results.

reference. The default searchtolerance is 0.

The output event table containsall of the input event table’sattributes, but the routeidentifier and measure locationinformation is from the targetroute reference.

You can choose to have theresulting table added to the mapas a feature layer, as astandalone table, or not at all.

��

ArcInfo

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CREATING AND EDITING EVENT DATA 143

Tip

Definition queriesWhen you transform events fromone route reference to another, anydefinition queries set up on theinput event layer will be respected.

Tip

Using the selectedfeaturesWhen you transform events fromone route reference to another, youcan choose whether you want toonly process the selected set offeatures.

9. Click the Browse button andnavigate to a location to savethe output event table.

Alternatively, you can typethe name and location of theoutput event table.

10. Type the names of the outputroute location fields if youwant to change thesuggested defaults.

11. Check whether you wouldlike to include all the fieldsfrom the input event layer.

12. Check whether you wouldlike the output table addedto the map as an event layer,as a standalone table, or notat all.

13. Click Finish.

ArcInfo

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Locating pointsalong routesYou can use the ArcMap RouteEvents GeoProcessing Wizardto create new point eventtables. The Locate pointfeatures along routes optionfinds the route and measureinformation of either all or aselected set of point featuresand writes them to a pointevent table in the workspace ofyour choice. This option is onlyenabled when there is one ormore point layers in your map.

To be located successfully, thepoints must be located on orwithin a specified tolerance ofthe routes. The default searchtolerance is 0. You control thesize of the search tolerance byspecifying a distance inwhichever units you prefer.

By default, the output eventtable contains the routeidentifier and measure locationof the route on which eachpoint falls, plus all of theattributes from the input pointfeature class. �

Locating point featuresalong routes

1. Click the Tools menu andclick Route EventsGeoProcessing Wizard.

2. Click Locate point featuresalong routes.

3. Click Next.

4. Click the point layerdropdown arrow and clickthe point layer to be located.

5. Click the Route Referencedropdown arrow and clickthe route layer.

6. Click the Route Identifierdropdown arrow and clickthe route identifier.

The route identifier uniquelyidentifies each route.

7. Type the search tolerance,click the dropdown arrow,then click the appropriateunits.

The tolerance defines howfar around each point thesearch will be done.

8. Click Next. �

Tip

Using a route referencethat is not in the mapUse the Browse button to navigateto the location of a route referencethat has not been added to the map.

��

ArcInfo

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CREATING AND EDITING EVENT DATA 145

Tip

Definition queriesWhen you locate points alongroutes, any definition queries set upon the input point layer will berespected.

Tip

Using the selectedfeaturesWhen you locate points along aroute, you can choose whether youwant to process only the selectedset of point features.

You can choose to not write outthe point attributes. In this caseonly the point’s OBJECTID fieldwill be written to the outputtable. This field can be used ata later time to join or relate backto the original point attributes.

If a point falls within a givensearch radius of more than oneroute, you can choose whetheronly the closest route locationor all route locations will bewritten to the output table.

You can choose to have theresulting table added to the mapas a feature layer, as astandalone table, or not at all.

9. Click the Browse button andnavigate to a location to savethe output event table.

Alternatively, you can typethe name and location of theoutput event table.

10. Type the names of the outputroute location fields if youwant to change thesuggested defaults.

11. Check whether you wouldlike to include a distancefield in the output table.

The values in the distancefield will be in the unitsspecified in Step 7.

12. Check whether you wouldlike to include only theclosest route location in theoutput table.

13. Check whether you wouldlike to include all the fieldsfrom the input point layer.

14. Check whether you wouldlike the output table addedto the map as an event layer,as a standalone table, or notat all.

15. Click Finish.

ArcInfo

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Locatingpolygons alongroutesYou can use the ArcMap RouteEvents GeoProcessing Wizardto create new line event tables.The Locate polygon featuresalong routes option computesthe route and measure informa-tion at the geometric intersec-tion of polygon data and routedata and writes them to a lineevent table in the workspace ofyour choice. This option is onlyenabled when there is one ormore polygon layers in yourmap.

By default, the output eventtable contains the routeidentifier and the from- and to-measure information of theroute upon which each polygonfalls, plus all of the attributesfrom the input polygon featureclass. You can choose to notwrite out the polygon at-tributes. In this case, only thepolygon’s OBJECTID field willbe written to the output table.This field can be used at a latertime to join or relate back to theoriginal polygon attributes.

You can choose to have theresulting table added to themap as a feature layer, as astandalone table, or not at all.

1. Click the Tools menu andclick Route EventsGeoProcessing Wizard.

2. Click Locate polygonfeatures along routes.

3. Click Next.

4. Click the polygon layerdropdown arrow and clickthe polygon layer.

5. Click the Route Referencedropdown arrow and clickthe route layer.

6. Click the Route Identifierdropdown arrow and clickthe route identifier.

The route identifier uniquelyidentifies each route.

7. Click Next. �

��

ArcInfo

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CREATING AND EDITING EVENT DATA 147

zero lengthline event

Tip

What is a zero length lineevent?A zero length line event occurswhen the from- and to-measuresare the same. This can happen inlocating polygons along routes, forexample, when a polygon touches aroute but does not overlap it.

Tip

Definition queriesWhen you locate polygons alongroutes, any definition queriesestablished on the input polygonlayer will be respected.

Tip

Using the selectedfeaturesWhen you locate polygons alongroutes, you can choose whether youwant to process only the selectedset of polygon features.

8. Click the Browse button andnavigate to a location tosave the output event table.

Alternatively, you can typethe name and location of theoutput event table.

9. Type the names of the outputroute location fields if youwant to change thesuggested defaults.

10. Check whether you wouldlike to include zero lengthline events in the outputtable.

11. Check whether you wouldlike to include all the fieldsfrom the input polygon layer.

12. Check whether you wouldlike the output table addedto the map as an eventlayer, as a standalone table,or not at all.

13. Click Finish.

� �

ArcInfo

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Editing eventtables in ArcMapYou can edit event attributes intwo ways: using the event’sattribute table or the Attributesdialog box.

As with editing the attributes ofany feature, editing eventattributes takes place within anedit session. You start an editsession by clicking StartEditing from the Editor menu onthe Editor toolbar. Once youbegin an edit session, you’llnotice this icon next to theOptions button on the tablewindow, indicating the tablecan be edited. In addition, �

Tip

Dynamic segmentationWhen displayed as a feature layer,editing an event’s route locationfield will cause the event’s locationto be dynamically resegmented.

Editing event recordsusing the table window

1. Click the Editor menu andclick Start Editing if you havenot started an edit session.

2. Open the event table youwant to edit.

You can open either astandalone event table orone that has been added toArcMap as a feature layer.For more information, see‘Adding route events’ inChapter 5.

3. Click the cell containing theattribute value you want tochange.

4. Type the value and pressEnter.

The table is updated.Tip

Adding the Editor toolbarTo display the Editor toolbar, clickTools and click Editor Toolbar.

Tip

Saving your edits oftenClick the Editor menu and clickSave Edits.

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CREATING AND EDITING EVENT DATA 149

Adding new eventrecords using the tablewindow

1. Click the Editor menu andclick Start Editing if you havenot started an edit session.

2. Open the event table youwant to edit.

3. Click the arrow on the right tomove to the end of the table.

4. Click a cell in the last recordand type in a new value.

Note: If your events table hasbeen added to ArcMap as afeature layer, the new eventwill appear on the map oncevalid route location valueshave been set. For moreinformation, see ‘Addingroute events’ in Chapter 5.

Deleting event recordsusing the table window

1. Click the Editor menu andclick Start Editing if you havenot started an edit session.

2. Open the event table youwant to edit.

3. Select the records you want todelete. Press and hold the Ctrlkey while clicking to selectmore than one record.

4. Press the Delete key on thekeyboard.

See Also

For more information on tableediting techniques, such as copyingand pasting records and makingsimple and advanced fieldcalculations, see Using ArcMap.

��

those fields that you can editwill have a white backgroundcolor for the field heading.

You make attribute changes byclicking a cell and typing a newvalue. If you make a mistake,you can easily undo the edit byclicking Undo from the Editmenu.

Editing attributes through thetable window allows you toquickly make changes toseveral records at once. Whenyou’re editing the attributes ofa specific event, you may find itmore convenient to use theAttribute dialog box, which isaccessed from the Editortoolbar. To use the Attributesdialog box with events, youmust first add your events toArcMap as a feature layer. Formore information, see ‘Addingroute events’ in Chapter 5.

The Attributes dialog box hastwo sides. The left side lists thefeatures you have selected.Features are listed by theirprimary display field and aregrouped by layer name. Theright side shows the attributefield names and their values. �

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Editing event recordsusing the Attributesdialog box

1. Click the Editor menu andclick Start Editing if you havenot started an edit session.

2. Click the Edit tool.

3. Select the events whoseattributes you want to edit.

4. Click the Attributes button.

5. Click the primary displayfield of the event feature forwhich you want to modify anattribute value.

6. Click the value you want tomodify.

7. Type a new value and pressEnter.

The attribute is modified forthe event feature.

Tip

Events as a feature layerFor events to be edited with theAttributes dialog box, they must bedisplayed in ArcMap as a featurelayer.

Tip

Noneditable tablesSome event tables cannot beedited—for example, delimited textfiles and tables accessed throughan OLE DB connection.

Tip

Noneditable fieldsIf you are editing your events afterthey have been added to the map asa feature layer, some fields will notbe editable. These are the fieldsthat are generated by the dynamicsegmentation process: Shape,Loc_Error, and Loc_Angle. �

� �

When you’ve completed youredits, you can save them andend the edit session.

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CREATING AND EDITING EVENT DATA 151

See Also

For more information on editingattributes with the Attributes dialogbox, see Editing in ArcMap.

Deleting event recordsusing the Attributesdialog box

1. Click the Editor menu andclick Start Editing if you havenot started an edit session.

2. Click the Edit tool.

3. Select the event you want todelete.

4. Click the Attributes button.

5. Right-click the primarydisplay field of the eventfeature you want to deleteand click Delete.

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153

12aliasAnother name for a field in a table.

attribute1. A piece of information describing a map feature. The attributes of a route might include its route

identifier, its measure length, the day it was built, and so on.

2. A column in a database table.

bookmarkSee spatial bookmark.

CADSee computer-aided design.

calibrationA procedure that recalculates route measures by first setting the measure value at known locations(points) and then interpolating and/or extrapolating all other measure values.

Catalog treeContains a set of folder connections in ArcCatalog that provides access to geographic data storedin folders on local disks or shared on a network. It also includes folders that let you managedatabase connections and coordinate systems. The Catalog tree provides a hierarchical view of thegeographic data in those folders.

computer-aided design (CAD)An automated system for the design, drafting, and display of graphically oriented information. Alsoknown as computer-aided drafting.

concatenate eventsCombines event records in tables where there are events on the same route that have the samevalue for specified fields; concatenate events will only combine events in situations where the to-measure of one event matches the from-measure of the next event. Concatenate events is availablefor line event tables only.

Glossary

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coordinate systemA method for specifying the location of real-world features on thesurface of the earth.

coverageA file-based vector data storage format for storing the location,shape, and attributes of geographic features. A coverage usuallyrepresents a single theme, such as soils, streams, roads, or landuse. It is one of the primary vector data storage formats forArcInfo.

database management systemA set of computer programs for organizing the information in adatabase. A database management system supports thestructuring of the database in a standard format and providestools for data input, verification, and storage.

dissolve eventsCombines event records in tables where there are events on thesame route that have the same value for specified fields; dissolveevents combines events when there is measure overlap. Dissolveevents is available for both line and point event tables.

dynamic segmentationThe process of computing the map location (shape) of eventsstored in an event table and displaying them on a map. Alsoknown as DynSeg.

edit sessionIn ArcMap, all editing takes place within an edit session. An editsession begins when you choose Start Editing from the Editormenu and ends when you choose Stop Editing.

Editor toolbarA set of tools that allows you to create and modify features andtheir attributes in ArcMap.

end hatch definitionA special type of hatch definition that draws hatch marks only atthe low and high measure of a linear feature.

eventSee route event.

event overlayAn operation that produces a route event table that is the logicalintersection or union of two input route event tables. Eventoverlay is one way to perform line-on-line, line-on-point, andevent point-on-point overlays.

event tableSee route event table.

event transformSee transform events.

extrapolationIn the context of linear referencing, this refers to the calculationof measure values on a route beyond where measure values arecurrently known.

featureA representation of a real-world object that can be displayed in alayer on a map.

feature classAn object class that stores features and has a field of typegeometry.

feature datasetA collection of feature classes that shares the same spatialreference.

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fieldA column in a table. Each field contains the values for a singleattribute.

geodatabaseAn object-oriented geographic database that provides servicesfor managing geographic data. These services include validationrules, relationships, and topological associations. A geodatabasecontains feature datasets and is hosted inside a relationaldatabase management system.

hatch classA container for hatch definitions.

hatch styleStores the symbols and settings of the hatch definitions thatmake up a hatch class.

hatchesA series of vertical line or marker symbols displayed on top offeatures at an interval specified in route measure units.

hatchingA type of labeling that is designed to post and label hatch marksor symbols at a regular interval along measured linear features.

indexCreated for an attribute or group of attributes in a feature class ortable to improve query performance. Feature classes can alsohave spatial indexes that improve spatial query performance.

interpolationIn the context of linear referencing, refers to the calculation ofmeasure values for a route between two known measure values.

intersectThe topological integration of two spatial datasets that preservesfeatures that fall within the area common to both input datasets.That is, intersect produces the logical AND between the inputdatasets. Compare with union.

joinThe process of attaching tabular data. The join process allowsdata from a layer or table (the join table) to be appended to aselected table or layer (the target table).

layerA collection of similar geographic features—such as highways,rivers, lakes, counties, or cities—of a particular area or place fordisplay on a map. A layer references geographic data stored on adata source, such as a shapefile, and defines how to display it.You can create and manage layers as you would any other type ofdata in your database.

line eventA feature that describes a portion of a route; it uses a from- andto-measure value. Examples include pavement quality, salmonspawning grounds, bus fares, pipe widths, and traffic volumes.

linear featureA geographic feature represented by a line. A line connects twoor more x,y coordinate pairs. Rivers, roads, and electric andtelecommunication networks are all linear features.

linear referencingA simplified method for storing geographic data by using arelative position along an already existing linear feature. Locationis given in terms of a known linear feature and a position, ormeasure, along it. Linear referencing is an intuitive way toassociate multiple sets of attributes to portions of linear features.

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linear referencing methodA way to identify a location along a route with respect to a knownpoint.

line-on-line overlayIn linear referencing, this involves the overlay of two line eventtables to produce a single line event table. The new event tablecan be the logical intersection or union of the input tables.

line-on-point overlayIn linear referencing, a line-on-point overlay involves the overlayof a line event table and a point event table to produce a singlepoint event table. The new event table can be the logicalintersection or union of the input tables.

mapA graphical presentation of geographic information. It containsgeographic data and other elements, such as a title, North arrow,legend, and scalebar. You can interactively display and query thegeographic data on a map and also prepare a printable map byarranging the map elements around the data in a visually pleasingmanner.

Map TipsDisplays onscreen descriptions of map features when you pausethe mouse pointer over the feature.

measureSee route measure.

measure location fieldsEither one or two fields in a table that describe the position of anevent along a route.

NaNNot a number.

OLE DB providerObject Linking and Embedding Database provider. Each providercommunicates with and retrieves data from a different database,but you can work with data retrieved by any provider in the sameway. Typically, providers can only retrieve nonspatial data.However, if an OLE DB provider can retrieve geographic data inOpenGIS format, you can work with that data in ArcInfo.

overlay eventsSee event overlay.

point eventA feature that occurs at a precise point location along a route; ituses a single measure value. Examples include accident locationsalong highways, signals along rail lines, bus stops along busroutes, and pumping stations along pipe lines.

point-on-line overlaySee line-on-point overlay.

polylineA two-dimensional feature representing a line containing one ormore line segments—that is, any line defined by three or morepoints. Line features, such as boundaries, roads, streams, andstreets, are usually polylines.

projectionA mathematical formula that transforms feature locations from theearth’s curved surface to a map’s flat surface. A projectedcoordinate system employs a projection or transforms locationsexpressed as latitude and longitude values to x,y coordinates.Projections cause distortions on one or more of these spatialproperties: distance, area, shape, and direction.

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GLOSSARY 157

rasterRepresents any data source that uses a grid structure to storegeographic information.

river addressingIn hydrology applications, another name for linear referencing.River addressing allows objects, such as field monitoringstations, which collect information about water quality analysis,toxic release inventories, drinking water supplies, flow, and so on,to be located along a river or stream system.

routeAny linear feature, such as a city, street, highway, river, or pipe,that has a unique identifier and a measurement system storedwith the geometry.

Route Editing toolbarA set of tools that allows you to create and modify routes inArcMap.

route eventA geographic feature occurring along a linear feature (route).There are two event types: line and point. A route event’s shapeis determined using dynamic segmentation.

route event sourceThe result of the dynamic segmentation process. A route eventsource serves an event table as a dynamic feature class. Everyrow in the table is served as a feature whose shape is calculatedwhen needed. For example, a route event source can act as thebasis of a feature layer in ArcMap.

route event tableA table that stores route locations and their attributes. A routeevent table, at a minimum, consists of a route identifier field and ameasure location field (point events) or fields (line events).

route feature classSee route reference.

route identifierA numeric or character value used to identify a route.

route locationA discrete location along a route (point) or a portion of a route(line). A point route location uses only a single measure value todescribe a discrete location along a route. A line route locationuses both a from- and to-measure value to describe a portion of aroute.

route measureA location along a route. Typically, a route measure is thedistance (in feet, meters, miles, and so on) from the start point of aroute. In some cases, however, measure values are nondistancebased (e.g., seismic shotpoints).

route measure anomaliesRoute measure values that do not adhere to the expectedbehavior. They can often be fixed with ArcMap route editingtools.

route referenceA collection of routes with a common system of measurementstored in a single feature class (e.g., a set of all highways in acounty).

scaleThe relationship between the dimensions of features on a mapand the geographic objects they represent on the earth,commonly expressed as a fraction or a ratio. A map scale of1/100,000 or 1:100,000 means that one unit of measure on the mapequals 100,000 of the same units on the earth.

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selected setA subset of features in a layer or records in a table. ArcMapprovides several ways to select features and records graphicallyor according to their attributes.

shapefileA vector data storage format for storing the location, shape, andattributes of geographic features. A shapefile is stored in a set ofrelated files and contains one feature class.

sketchA shape that represents a feature’s geometry. Every existingfeature on a map has an alternate form—a sketch. A sketch letsyou see exactly how a feature is composed with all vertices andsegments of the feature visible. To modify a feature, you mustmodify its sketch.

snapping environmentThe automatic intersecting of disjointed lines or nodes that arisewhen map data is being digitized or scanned.

spatial bookmarkIn ArcMap, identifies a particular geographic location that youwant to save and refer to later—for example, a study area.

spatial domainDescribes the range and precision of x,y coordinates and z- andm-values that can be stored in a feature dataset or feature class ina geodatabase.

spatial referenceDescribes both the projection and spatial domain for a featuredataset of a feature class in a geodatabase.

SQLStructured Query Language. A syntax for defining andmanipulating data from a relational database. Developed by IBMin the 1970s, it has become an industry standard for querylanguages in most relational database management systems.

stationingIn the pipeline industry, another name for linear referencing.Stationing allows any point along a pipeline to be uniquelyidentified.

Structured Query LanguageSee SQL.

symbolA graphic pattern used to represent a feature. Manycharacteristics define symbols, including color, size, and shape ofthe symbol used.

tableA set of data elements that has a horizontal dimension (rows) anda vertical dimension (columns) in a database. A table has aspecified number of columns but can have any number of rows.

topologyThe model used to describe how features share geometry. It isalso the mechanism for establishing and maintaining topologicalrelationships between features and feature classes. ArcGISimplements topology through a set of validation rules thatdefines how features share geographic space and a set of editingtools that works with features that share geometry in anintegrated fashion.

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transform eventsAn operation that produces a new table by copying andtransforming events from one route reference to another. Thisallows the events to be used with a route reference havingdifferent route identifiers and/or measures.

unionThe topological integration of two spatial datasets that preservesfeatures that fall within the area common to either input dataset.That is, union produces the logical OR between the inputdatasets. Compare with intersect.

Universal Transverse MercatorSee UTM.

UTMUniversal Transverse Mercator. A projected coordinate systemthat divides the world into 60 north and south zones, six degreeswide.

vectorA coordinate-based data structure commonly used to representlinear geographic features. Each linear feature is represented asan ordered list of vertices.

vector modelA representation of the world using points, lines, and areas.Vector models are useful for representing and storing discretefeatures, such as buildings, pipes, or parcel boundaries.

vertexA point that joins two segments of a feature.

wizardA tool that leads a user step by step through an unusually long,difficult, or complex task.

workspaceA container for geographic data. This includes a folder thatcontains shapefiles, an ArcInfo workspace that containscoverages, a personal geodatabase, or an ArcSDE databaseconnection.

zero length line eventA line event whose from-measure is equal to its to-measure. Thiscan happen, for example, when locating polygons along routesand the polygon touches a route but does not overlap it.

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12Index A

Aliasdefined 153

ArcCatalog 47, 48, 70, 73ArcInfo Workstation 48ArcSDE

storing routes 48ArcToolbox 47, 48, 73

calibrating routes with points 67creating routes from existing lines 61

Attributes 5defined 153storing multiple sets 42

B

Bookmark. See Spatial bookmark

C

CAD (Computer-aided design) 61, 68defined 153input feature class 11

Calculating route measures with points. SeeCalibrating routes

Calibrate Routes Wizard 11, 68, 70Calibrating routes

described 50, 67, 117digitizing points

order of 118undoing 117

disjointed routes 51, 118using measure distance 51, 67using shortest path distance 50, 67

Calibrationdefined 153

Catalog treedefined 153

Complex routecreating 113

Computer-aided design 153. See CADConcatenate events

defined 153described 128

Convert Hatches to Graphics commandadding 96

Coordinate priority 48Coordinate system

defined 154described 43

Coordinates or measures out of bounds 114Coverage

defined 154Coverage route system

migrating to a geodatabase 73–76Coverage to Geodatabase tool

in ArcToolbox 73Create Routes Wizard 11, 62, 63

D

Dataorganizing

in ArcCatalog 10storing

as a multipoint feature 40as a point feature 40as a polygon feature 40as a polyline feature 40

Database management systemdefined 154

Decimalsnumber displayed 123

Definition queries 140, 143Display symbol

changing 20Dissolve events

described 128Dissolve operation

defined 154

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Dynamic segmentation. See also Route eventsadvanced options 108defined 154described 40, 105using attribute indexes 107

E

Edit sessiondefined 154

Edit Sketch Properties 121Editor toolbar

adding 110, 148defined 154

Editssaving 38, 148

End hatch definitiondefined 154described 83view 88

Event. See also Route eventsdefined 154

Event dataaggregating 128editing 131storing

in dBASE tables 126in geodatabases 126in INFO tables 126in text files 126

Event layerssaving 108

Event measurestransforming 129, 141–142

with the field calculator 141updating 129

Event overlaydefined 154

Event recordsadding

using the table window 149

Event records (continued)deleting

using the table window 149with the Attributes dialog box 151

editingusing the Attributes dialog box 150using the table window 148

Event table. See also Route event tablesdefined 154

Event transform. See also Route eventsdefined 154

Events. See Route eventsExisting routes

editing 119Extrapolation

defined 154

F

Feature classdefined 154described 43using as a template 55

Feature datasetdefined 154described 43with multiple route feature classes 43

Featuresdefined 154described 1modifying 121splitting or merging 41storing as relative locations 41

Field names 76Fields

calculating 141defined 155noneditable 150

Folder connectioncreating 10

From/To measuressetting 122

G

Geodatabasedefined 155

Geographic datamodeling 40

Graphicssaving 98

Grid size 53

H

Hatch classassociating a SQL query 92defined 155described 83removing 95saving as a hatch style 102view 86

Hatch definitioncopying 95view 87

Hatch Orientation dialog box 90Hatch Placement Options dialog box 89Hatch style

applying to a hatch class 103creating in the Style Manager 101defined 155described 101saving 102

Hatch Style dialog boxaccessing 102

Hatches 91–92converting to graphics 96, 98creating and managing 85defined 155described 91–92displaying 91generating text with a script 99importing 94intervals of 84

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Hatches (continued)manipulating text 99nonappearing 93overlapping with labels 93scaling with the map 94stopping the drawing process 93

Hatchingdefined 155described 83distance-based measures 83nondistance-based measures 83options 84

I

Id fielddeleting 60

Identify Route Locations tooladding 22, 79not enabled 80

Indexdefined 155

Input widthdescribed 134

Interpolationdefined 155

Intersectdefined 155events. See Overlay events

J

Joindefined 155

L

Label Settings dialog box 90Layer

defined 155described 77

Layer dropdown listusing 80

Line eventdefined 155described 44displaying on a map 28. See also Dynamic

segmentationLine-on-line overlay

defined 156. See also Overlay eventsLine-on-point overlay

defined 156. See also Overlay eventsLinear feature

defined 155described 39

Linear referencing 45defined 155described 39highways and streets 2oil and gas exploration 5pipelines 6railways 4transit 3water resources 7

Linear referencing methoddefined 156described 45

M

M domainchoosing 52

Make Route commanddescribed 34, 112

Mapdefined 156

Map documentexisting

opening 19Map Tips

defined 156remeasuring portion of a line 123

Measure distance. See Calibrating routesMeasure location fields

defined 156Measures. See also Route measures

defined 156described 40, 43out of bounds 114setting as distance 121unknown (NaN) 43

N

NaNcalculating 120defined 156described 43

O

OBJECTID field 133, 137OID field 134OLE DB provider

defined 156Overlapping segments

preserving 116Overlay events. See also Route events

defined 156line-on-line 126line-on-point 127

P

Point eventsdefined 156described 44displaying on a map 27. See also Dynamic

segmentationPoint features

locating along routes 130, 144–145Point-on-line overlay

defined 156

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Polygon featureslocating along routes 131, 146–147

Polylinedefined 156described 43storing a measurement system 43with multiple, connected paths 43with multiple, disjointed paths 43with one path 43

Precision 56, 64Projection

defined 156

R

Rasterdefined 157

Reference scalesetting 94

Route dataadding to a map 20, 32calibrating 15creating 11

measure values are known 49measure values are not known 48

migratingto a geodatabase 73–74

querying 79Route Editing toolbar

addingusing the Customize dialog box 110using the Editor menu 110

defined 157Route event. See also Route events

defined 157Route event source

defined 157Route event tables

automated techniques 126concatenating 128

Route event tables (continued)creating

in a geodatabase 132–133in ArcCatalog 132–133in dBASE 134in INFO 135

defined 157described 44, 125dissolving 128editing in ArcMap 148–149intersecting 127

Route eventsadding to a map 107. See also Dynamic

segmentationaggregating 139described 44, 107displaying 107dissolving and concatenating 139–140editing 148overlaying 136–137

intersect 136union 137–138

querying 29transforming 142–143

Route Events GeoProcessing Wizardaggregating events 139. See also Dissolve

events, Concatenate eventslocating points along routes 144–145. See

also Point featureslocating polygons along routes 146–147. See

also Polygon featuresoverlay events 136. See also Intersect,

Uniontransforming events 142–143. See also

Transform eventsRoute feature class

creatingin a geodatabase 54in an existing feature dataset 57

defined 157

Route identifiercreating an index 57, 59defined 157described 78saving 78setting 21, 35, 78, 82values 80

Route locationdefined 157described 44, 107finding 24, 82identifying 23, 80labeling 81

Route measure. See also Route measuresdefined 157

Route measure anomaliesdefined 157described 25, 104displaying 25, 104

using a scale range 104using a SQL query 104

Route measure unitsconverting 36

Route measures. See also Measurescalculating using points 50. See also

Calibrating routesediting

with an edit sketch 121setting 119

using Apply Factor 120using Calculate NaN 120using Drop Measures 120using Offset 120using Set As Distance 119using Set Direction as M 120using Set From/To 120

Route reference. See also Linear referencingmethod

defined 157multiple 129using one not in the map 144

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Route structure 142Routes

calibrating with points 67–69creating 111

by merging linear features 48from existing lines 61–62

defined 157described 43, 48editing 32making from selected features 34, 111realigning 122recalibrating 37remeasuring 123storing 48

S

Scaledefined 157

Segmented data 41Selected set

defined 158Shapefile

creating to store routes 58defined 158

Shortest path distance 67. See Calibratingroutes

Shotpointdescribed 5

Simple routecreating 111

Sketchdefined 158

Snapping environmentdefined 158

Spatial bookmarkdefined 158

Spatial domaindefined 158

Spatial referencedefined 158

SQLdefined 158

Standalone feature classcreating to store routes 54–57

Starting priority. See Coordinate priorityStationing

defined 158Storing routes 48Symbol

defined 158

T

Tabledefined 158noneditable 150

Target annotationnonappearing 98

Target feature classsetting 33

Tolerancechoosing 142

Toolbarsadding 33

Topology 45defined 158described 45with multiple linear referencing methods 45

Transform events. See also Route eventsdefined 158

U

Uniondefined 159events. See Overlay events

Universal Transverse Mercator (UTM)defined 159

UTM (Universal Transverse Mercator)defined 159described 43

V

Vectordefined 159described 40

Vector modeldefined 159described 41

Vertexdefined 159

W

Wizarddefined 159

Workspacecreating 135defined 159

Z

Zero length line eventdefined 159described 147

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