Geodatabases in GISGeodatabases in GIS

Engineering Geographic Information SystemsEngineering Geographic Information Systems

CIVE 7397CIVE 7397

Spring 09 Spring 09

Introduction Introduction

In ArcGIS, there are three basic data structures:

shapefiles, coverages, and geodatabases

A A geographicgeographic data modeldata model is is a structure for organizing a structure for organizing geospatial data so that it can geospatial data so that it can be easily stored and be easily stored and retrieved.retrieved.

Geographic coordinates

Tabular attributes

Data ModelsData Models

CoveragesCoverages Developed for Developed for

workstation Arc/Info workstation Arc/Info ~ 1980~ 1980

Complex structure, Complex structure, proprietary formatproprietary format

Attributes in Attributes in Info Info tablestables

ShapefilesShapefiles Developed for Developed for

ArcView ~ 1993ArcView ~ 1993 Simpler structure in Simpler structure in

public domainpublic domain Attributes in Attributes in dBase dBase

(.dbf) tables(.dbf) tables

Geographic coordinates and attributesare stored in separate but linked files

ArcInfo

File-based Data ModelsFile-based Data Models

Coverages Shapefiles

Texas

Counties.shpCounties.shxCounties.dbfEvap.shpEvap.shxEvap.dbf

Storing Data Storing Data

Texas

Evap

Info

Counties

Coverages and ShapefilesCoverages and Shapefiles Coverages are stored partially in their own folder and Coverages are stored partially in their own folder and

partially in the common INFO folder. Shapefiles are partially in the common INFO folder. Shapefiles are stored in three to five files (with stored in three to five files (with extensions .shp, .shx, .dbf, .sbx and .sbn)extensions .shp, .shx, .dbf, .sbx and .sbn)

Coverages store common boundaries between Coverages store common boundaries between polygons only once, to avoid redundancy. Shapefiles polygons only once, to avoid redundancy. Shapefiles store all the geometry of each polygon regardless of store all the geometry of each polygon regardless of redundancyredundancy

Coverage features are single lines or single polygons. Coverage features are single lines or single polygons. Shapefiles allow features to have multiple, Shapefiles allow features to have multiple, disconnected, intersecting and overlapping disconnected, intersecting and overlapping componentscomponents

Storing Data Storing Data - - Cont’dCont’d

A geodatabase is a relational database that stores geographic information

It is a data storage and management framework for storing and manipulating spatial, geographic and attribute information

Geodatabase and Feature DatasetGeodatabase and Feature Dataset

Geodatabase StructureGeodatabase Structure

Source: ESRI

Feature class: Contains geographic information of geometric type (points, polygons, and lines) and spatial reference

Feature datasets: A group of feature classes forms a feature dataset

Non spatial tables: These do not contain any spatial attributes but can be connected to tables that have spatial information

Geodatabase

Feature Dataset

Feature Class

Geometric Network

Object Class

Relationship

Workspace

ArcGIS GeodatabaseArcGIS Geodatabase

Why the Geodatabase Why the Geodatabase

Geodatabases can be used to manage raster datasets

Scalability: Can create a personal geodatabase or a geodatabase for the enterprise

Attributes can be easily created and maintained

Geometric networks can be created for path finding analysis

AnAn object classobject class is a collection of is a collection of objectsobjects in in tabular formattabular format that that have the same behavior and the same attributes.have the same behavior and the same attributes.

An object class is a table that has a unique identifier (ObjectID)for each record

Object ClassObject Class

AA feature classfeature class is a is a collection of collection of geographic geographic objectsobjects in in tabular formattabular format that have the same that have the same behavior and the same behavior and the same attributesattributes

Feature Class = Object class + spatial coordinates

Feature ClassFeature Class

A A relationshiprelationship is a is an association or link between n association or link between two objects in a databasetwo objects in a database

A relationship can exist between spatial objects A relationship can exist between spatial objects (features in feature classes), non-spatial objects (features in feature classes), non-spatial objects (objects in object classes), or between spatial (objects in object classes), or between spatial and non-spatial objectsand non-spatial objects

RelationshipRelationship

Relationship between non-spatial objects

Water QualityData

Water Quality Parameters

RelationshipRelationship

Relationship between spatial and non-spatial objects

Water quality data(non-spatial)

Measurement station

(spatial)

RelationshipRelationship

Populating the GeodatabasePopulating the Geodatabase The following file types can be imported into a The following file types can be imported into a

geodatabase:geodatabase: Shapefile, Coverage, Raster, CAD, Feature Shapefile, Coverage, Raster, CAD, Feature

classclass

The following file types can be exported from The following file types can be exported from a geodatabase:a geodatabase:

Shapefile, Coverage, XML, Raster, Feature Shapefile, Coverage, XML, Raster, Feature classclass

Generating New DataGenerating New Data Scanning data: Produces a raster image which Scanning data: Produces a raster image which

can be georeferenced after scanningcan be georeferenced after scanning

Digitizing imageDigitizing image

Geographic Coordinate System

Projected Coordinate System

Coordinate Domains

Creating a New Feature ClassCreating a New Feature Class

Need to define geometry type (line, point etc), Need to define geometry type (line, point etc), spatial reference, fields in the attribute tablespatial reference, fields in the attribute table

Feature Class PropertiesFeature Class Properties

Need to define geometry type (line, point etc), Need to define geometry type (line, point etc), spatial reference, fields in the attribute tablespatial reference, fields in the attribute table

Validating the GeodatabaseValidating the Geodatabase Defining Subtypes and DomainsDefining Subtypes and Domains

• Subtype: Subset of a record within a fieldSubtype: Subset of a record within a field• Domain: Coded value or range domainDomain: Coded value or range domain

Feature class

Streets Pipe

LocalSubtypes Highway Concrete Steel

Domains BLVD, RD, AVE

HWY, FWY

Diameter10 – 14 Inch

Diameter> 14 Inch

TopologyTopology Define spatial relationships between featuresDefine spatial relationships between features --- Connectivity, Adjacency, Coincidence--- Connectivity, Adjacency, Coincidence --- Between one or more features--- Between one or more features Maintains spatial integrity by setting rules for Maintains spatial integrity by setting rules for

overlapping, intersecting etcoverlapping, intersecting etc

Examples:Examples:

Connectivity: Streams, streetsConnectivity: Streams, streetsAdjacency: Land parcels, municipal districtsAdjacency: Land parcels, municipal districtsCoincidence: BoundaryCoincidence: Boundary

Examples of GeodatabasesExamples of Geodatabases

City of Houston needs to design a geodatabase for transportation infrastructure development and construction of a new Metro rail.

What layers/files/tables would the geodatabase contain?

Highways Major roads Rail routes

Traffic Zone Analysis Traffic Hot spots Congested routes Commute time