Copyright © 2005 Bruce Kessler All Rights Reserved Ch. 2 GeoDatabase Basics Laying the foundations

Copyright © 2005 Bruce Kessler All Rights Reserved

Ch. 2GeoDatabase Basics

Laying the foundations

Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-2

Goals

HistoryBenefits / disadvantagesFeature geometryTypes of GeoDatabasesManaging a GeoDatabase

– Structure– Spatial reference


GeoDatabase History/Description/AdvantagesMost of the structure was developed before ArcGIS

Desktop softwareThe framework for vector, raster, and tabular data

storage in ArcGISUnique data formatMethod for storing spatial and attribute data as well as

other types of data (raster, tables, relationships, etc.)Has integrity rulesHas operatorsMethod for supporting transactional views: versionsA means for modifying object behavior


Before Using A GeoDatabase

Buy a full set of manuals!!!!Research your topics using White PapersKnow how to and use the on-line help

resources from ESRI – especially the Forums

A


Benefits of a GeoDatabase

Centralized managementLarge data management in a continuous

integrated environment: raster/vector/tabular/CAD (SDE)

Multi-user editing (SDE)



Topology– Complex geometric networks – Geometric relationships within and between multiple

feature classes

Maintained through rules – simple polygon example



Create and edit topologically integrated features with automatic maintenance

Easily control exceptions to ruleSupport of advanced data types:

measures, functional curves, Z valuesFeature-linked annotation


Benefits of a Geodatabase

Efficient data entry with rules, relationships, and behavior

Schema can be developed with CASE tools

Custom objects


Review of Feature Geometry

PointMulti-pointLine

– User-shaped– Curves– Single / multi-part

Polygon– Single / multi-part


Review of Feature Coordinates

X, Y – this is easyZ

Elevation

M

Measure


Two types of GeoDatabases

Personal– Access

Multi-user– SDE


GeoDatabase (GDB) structure

Stores– Feature datasets– Feature classes– Tables– Raster– More

A unique structure within the GDB


GDB Objects: Feature Class (FC)

A collection of features– Each feature class has one geometry type (point,

multi-point, line, polygon)Can be stored in a feature dataset or ‘stand-alone’Attributes are

stored with coordinate data in one table


Spatial Reference

Property of a feature class or feature datasetComponents

– Coordinate system– Coordinate domain

Permanent after definition is saved– Warning: it may look like you changed the

coordinate system, but you can’t and don’t try. It messes things up!

See next slide for more information


Spatial Reference

A


Coordinate domainExtent of available coordinates

– Min and max X,Y coordinates– Precision = storage units per

map unitExample, 1000 mm per meter

Make sure it covers study area– Allow for growth

ArcCatalog default– Import: data plus room for growth

Set your own– Import from existing data– Type in extent for study area

2.14 billion storage units


Accuracy and PrecisionAccuracy in the Data

– Scale of source map scale will determine accuracy*1:600 (1”=50’) ± 1.7 feet1:1,200 (1”=100’) ± 3.33 feet1:2,400 (1”=200’) ± 6.67 feet 1:4,800 (1”=400’) ± 13.33 feet 1:24,000 ± 40.00 feet

– PrecisionAbility to store the accuracy

– Significant digits• Single precision 6-7 precise digits• Double precision 13-14 precise digits• Geodatabase 0-10 precise digits


Domain

A property of a feature dataset or feature class (cannot change once set)


Standard FieldsFeature classes have default fields

– ObjectID – unique identifier– Shape – contains coordinates of feature– Area – automatically calculated and maintained for polygons

Shape_Area (Personal GDB)

– Length – automatically calculated and maintained for lines and polygons

Shape_Length (Personal GDB)


GDB Objects: Feature Dataset

A collection of feature classes– Environment for spatial reference– Environment for topology – Environment for coincident geometry and linked

annotation– Feature classes inherit spatial reference

Data loaded are projected on the fly, if necessary


Managing Your GDB

ArcCatalog is your main tool to manage the schema– Construction of component parts– Organization of those parts– Properties for the parts

Many capabilities are available– Some are not on the default GUI


Creating a GDB

Personal– Use ArcCatalog

Multi-user– Must be done at the

system level A


Creating an empty feature class

Two locations available: stand-alone and within a feature dataset

A


Creating a feature dataset

A


Tips

Projecting data– Must create a new feature class

PGDB is 2 GB maxRead-only on a PGDB will restrict some

analyses, such as Select by LocationUse compact to clean up temporary filesAll table names need to be unique


Ex 2

Create a Personal GDBCreate an empty Feature ClassCreate a Feature DatasetCreate a Feature Class within the

Feature Dataset

Documents

Copyright © 2005 Bruce Kessler All Rights Reserved Ch. 2 GeoDatabase Basics Laying the foundations