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Geodatabases in GIS Engineering Geographic Information Systems CIVE 7397 Spring 09

Geodatabases in GIS Engineering Geographic Information Systems CIVE 7397 Spring 09. Introduction. In ArcGIS, there are three basic data structures: shapefiles, coverages, and geodatabases.

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Geodatabases in GIS Engineering Geographic Information Systems CIVE 7397 Spring 09

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  1. Geodatabases in GISEngineering Geographic Information SystemsCIVE 7397Spring 09

  2. Introduction In ArcGIS, there are three basic data structures: shapefiles, coverages, and geodatabases

  3. A geographicdata modelis a structure for organizing geospatial data so that it can be easily stored and retrieved. Data Models Geographic coordinates Tabular attributes

  4. Coverages Developed for workstation Arc/Info ~ 1980 Complex structure, proprietary format Attributes in Info tables Shapefiles Developed for ArcView ~ 1993 Simpler structure in public domain Attributes in dBase (.dbf) tables File-based Data Models Geographic coordinates and attributes are stored in separate but linked files Arc Info

  5. Storing Data Texas Texas Counties Counties.shp Counties.shx Counties.dbf Evap Evap.shp Evap.shx Evap.dbf Info Coverages Shapefiles

  6. Coverages and Shapefiles Coverages are stored partially in their own folder and partially in the common INFO folder. Shapefiles are stored in three to five files (with extensions .shp, .shx, .dbf, .sbx and .sbn) Coverages store common boundaries between polygons only once, to avoid redundancy. Shapefiles store all the geometry of each polygon regardless of redundancy Coverage features are single lines or single polygons. Shapefiles allow features to have multiple, disconnected, intersecting and overlapping components Storing Data - Cont’d

  7. Geodatabase and Feature Dataset • Ageodatabaseis a relational database that stores geographic information • It is a data storage and management framework for storing and manipulating spatial, geographic and attribute information

  8. Geodatabase Structure • 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 Source: ESRI

  9. ArcGIS Geodatabase Workspace Geodatabase Feature Dataset Feature Class Geometric Network Relationship Object Class

  10. 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

  11. Anobject classis a collection of objects in tabular format that have the same behavior and the same attributes. Object Class An object class is a table that has a unique identifier (ObjectID) for each record

  12. Afeature classis a collection of geographic objects in tabular format that have the same behavior and the same attributes Feature Class Feature Class = Object class + spatial coordinates

  13. A relationship is an association or link between two objects in a database A relationship can exist between spatial objects (features in feature classes), non-spatial objects (objects in object classes), or between spatial and non-spatial objects Relationship

  14. Relationship Relationship between non-spatial objects Water Quality Data Water Quality Parameters

  15. Relationship Relationship between spatial and non-spatial objects Water quality data (non-spatial) Measurement station (spatial)

  16. Populating the Geodatabase • The following file types can be imported into a geodatabase: Shapefile, Coverage, Raster, CAD, Feature class • The following file types can be exported from a geodatabase: Shapefile, Coverage, XML, Raster, Feature class

  17. Generating New Data • Scanning data: Produces a raster image which can be georeferenced after scanning • Digitizing image Geographic Coordinate System Projected Coordinate System Coordinate Domains

  18. Creating a New Feature Class • Need to define geometry type (line, point etc), spatial reference, fields in the attribute table

  19. Feature Class Properties • Need to define geometry type (line, point etc), spatial reference, fields in the attribute table

  20. Validating the Geodatabase • Defining Subtypes and Domains • Subtype: Subset of a record within a field • Domain: Coded value or range domain Streets Pipe Feature class Local Concrete Steel Highway Subtypes BLVD, RD, AVE HWY, FWY Diameter > 14 Inch Diameter 10 – 14 Inch Domains

  21. Topology • Define spatial relationships between features --- Connectivity, Adjacency, Coincidence --- Between one or more features • Maintains spatial integrity by setting rules for overlapping, intersecting etc Examples: Connectivity: Streams, streets Adjacency: Land parcels, municipal districts Coincidence: Boundary

  22. Examples 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

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