geodatabases in gis engineering geographic information systems cive 7397 spring 09
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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