Esri Clsa2006

1. ESRIs Cadastral Extension to Survey Analyst

This presentation will describe development work currently underway for the new Cadastral Extension to Survey Analyst.

ALICE Project

Introduction and Overview

System Design and Concepts

Links with NSRS and CRTN

To build a simple extension toArcGISto improve and maintain the positional accuracy of boundary geometry and associated GIS layers.

Multipurpose GIS is often pinned on the cadastral layer

Cadastral base map governs other associated GIS layers

Accurate and consistent spatial data significantly extends GIS usefulness

GPS enabled systemsAREubiquitous

GIS currently provides comprehensive underlying mapping information

But to make GIS more useful and GPS more valuable,this information must be accurate

GIS needs to improve here!

Survey Analyst Cadastral Extension:

Is extendable (data models & tools)

Follows survey methods for managing geometry

Incrementallyimproves positional accuracy ofexisting GIS datasets

Maintains spatial relationships between theCadastral base map and associated GIS layers

Cadastral fabric geometry

+ geodetic control coordinates

+ weighted least-squares adjustment

+ accumulated displacement vectors

= ACCURATE FEATURE LAYERS

The fabric is acontinuous surfaceof connected parcels

It is also a dimensionedboundary network

Followsexplicit geometric constraintssuch as common parcel corners

Parcels are also constrained by their relation to other parcels

Constraints are inherent in the model andenforcedduring data entry

Once upon a timemeasuring bearing and distance was easier than fixing a position

So land surveys are described by parcel dimensions

Precision of these measurements is generally known

So, measures and connections were known, but true coordinates were not

Most LIS databases derived from scanning or heads-up digitizing of plat maps

Accuracy poor even after rubber-sheeting to control

Most importantly, original record measures are stored but not used

Instead, they are often distorted after a rubber-sheeting adjustment

We need accurate coordinates for thefabric and associated GIS layers

Accurate fabric coordinates are derived from:

geodetic control

survey measurements

Like control, fabric points have:

A physical location (monument)

Reliability information (level of confidence)

A dimensioned cadastral fabric can be made very accurate using limited control

A least-squares adjustment uses all of the survey information, including historic, to distribute error

In Cadastral Extension, coordinates are a derived quantity, stored as a transient attribute of a point rather than a definition of the point

Coordinates as attributes meanshistorical coordinatescan be retained, just like historical survey measurements

Datumre-adjustments andepoch updatesare facilitated when measurements are retained and used in a least-squares adjustment

Often, associated GIS layers are created and maintained in context with the cadastre

An accurate cadastre then can serve ascontrolfor the rest of the GIS

If we capture the shifts in coordinates of the parcel corners

we can use these to adjust the associated layers and maintain spatial relationships

The result is more accurate coordinates all around

Measurement Cadastres

Survey measurements have definitive role

Specifically designed for this

Coordinated Cadastres

Use fabric and geodetic control to move from measures to coordinates

Customize to work with coordinates as the source

DifferentiateSourceinformation fromDerivedinformation

DifferentiateSurvey Rulesinformation fromGIS Rules

Parcelsare the basic unit of work

Create and editparcels

Joinparcelsto the fabric

Control pointsfixandgeo-reference the fabric

Connected (and historic) parcels provideredundancy of measurements

Fabricnetworkis constrained to control points and adjusted byleast-squares

Parcels updated with new record information are never deleted from the fabric, they are simply marked asHistoric

4 different types of historic information maintained:

State of the Cadastre on a particular date

State of the Fabric on a particular date

Lineage of aParcel

History of adjustments to the fabric

Parcel is unit of work

Parcels are created by entering a loop traverse of the parcel boundary

Parcel closure is reported on-the-fly

At this stage corner coordinates are in an arbitrary local coordinate system

Joining is an interactive point and click operation

Match shared points

Automatic 2D translation-rotation-scale performed

From local project coordinate space

To projected coordinate space (SPCS)

Additional Q/C checkprovided by the transformation residuals resulting fromJoining

Parcel Joiningenforcesthe cadastral specificgeometric constraintsbetween parcels

Joining is the easiest and fastest way to build the fabric

Joining ensures best fit to the existing fabric

No slivers or overlaps possible

Can transfer basis-of-bearing

Provides approximate coordinates needed by the adjustment

Fabric + Control + LSA = Good Coordinates

LSA does more than improve coordinates

Shows where control is needed

Helps isolate errors in the data (e.g. incorrectly entered measurements)

Post-adjustment analysis reports

LSA only estimates coordinates,never changes the original measurement values

After LSA the software creates a set of adjustment vectors

Each points coordinate residual generates a vector

This in turn generates a residual vector field

Vector sets are stored as a history of coordinate shifts based on each sequential LSA

GIS layers may be adjusted using the vector field

You decide when to adjust a GIS layer to the fabric

This is possible because the fabric maintains its adjustment history via the vector field

A cadastral fabric that is:

Accurateto the same mathematical integrity as the original survey measurements

Completeby preserving all observed data

Coordinatedin the NSRS

AGIS databaseof original survey measurements

Ability to correctlygeo-referenceGIS feature layers to the fabric

Ability to keep apace with NSRSre-adjustments and epoch updatesusing LSA

Original data are preserved

Data model adheres to cadastral specific geometric constraints

Provides incremental accuracy improvements:

Of the fabric

Of associated GIS feature layers

Highly user customizable with a simple model

Deep integration withArcGIS

Zilkoski, D. & D. D'Onofrio.GEODETIC PHASE OF NOS' SAN FRANCISCO BAY DEMONSTRATION PROJECTstates:

Explicit ObjectivesA modernized height system primarily based on the CORS willensure a common foundation for all spatially related geographic data , including land and marine GIS data, and provide reliable height information for FEMA's Flood Plain Mapping program and for local surveyors, engineers, and planners. It will alsosupport GIS requirements for regional and national transportation GISs , and provide data critical to monitor watershed planning and protection.

THE CONTRIBUTION OF GEODETIC DATA TO THE NATIONAL SPATIAL DATA INFRASTRUCTURE

Rear Admiral J. Austin Yeager, NOAA, Director, Coast and Geodetic Survey; Captain Lewis A. Lapine, NOAA Chief, National Geodetic Survey, C&GS; and John F. Spencer, Jr., Chief, National Geodetic Information Branch, NGS states:

In the 1993 National Research Council (NRC) report,Toward a Coordinated Spatial Data Infrastructure for the Nation(1), it was exemplified that geodetic control is requiredto systematically register all spatial information to allow their integration into Geographic Information Systems (GIS).Such GIS systems have application in wetlands delineation, mineral assessment, renewable resource management, public health, urban and regional planning, disaster response and recovery, and national defense, among others.

But the mere application of geodesy alone

doesnt create order out of chaos. Geodesy

shapes our lives today through a combination of

three innovative tools:

the Global Positioning System(GPS), which

supplies the coordinates;

NOAAsNational Spatial Reference System

(NSRS), which gives the GPS coordinates

integrity; and

Geographic Information Systems (GIS), which make the coordinates useful.

As our society and economy become increasingly

dependent on complex technologies, the

need for precise positioning and consistent, reliable

data intensifies. This imaginative trio of GPS,

NSRS, and GIS is providing the order needed for

ensuring public safety, enhancing economic

prosperity, and protecting environmental quality

throughout the nation.

Survey Analyst for CadastreswithLow Distortion Projections (LDP)

LDP is a mapping projection that minimizes the difference between distances depicted in a GIS when compared to the real-world distances at ground elevation

Standard mapping projections are at sea level (ellipsoid)

Distortion increases with elevation

NGS is considering supporting registered LDP as an addition to theirGeodetic Tool Kit

The value of a GIS increases directly as a function of itsaccurateportrayal of items of interest

Local govt. GIS managers are realizing the benefits of incorporating survey measurements (COGO)

Leads to better decision support from the GIS

There is virtually no cost to using LDP in GIS

On-the-fly re-projection is routine in ArcGIS

Standard Projections are not good enough for local GIS

UTM distortion is 1:2,500 (2.1 ft per mile)

SPC distortion is 1:10,000 (0.5 ft per mile)

But in both cases distortion at ground usually much greater

Local GIS will increasingly use LDP for their data

The fundamental purpose of the NSRS is to support mapping

SPCS is not adequate for many applications

Use of well-defined registered projections can encourage use of the NSRS rather than local control

OPUS option for positions in LDP coordinates

Data sheets could include LDP coordinates

The LDP tool encourages state and local government to utilize the NSRS as their GIS basis

Eventually LDP will replace current SCPS in state regulations

Most of the nations infrastructure our

transportation, utility, energy, and communications

systems depends on the teamwork provided

by GPS, GIS, and the National Spatial Reference

System.

380 New York St., Redlands, CA

Kevin M. Kelly, Geodetic Engineer

[email_address] ; 909-793-2853 x1162

Tim Hodson, Product Engineer

[email_address] ; 909-793-2853 x2077

Business

Esri Clsa2006