1. Geodatabases in GIS Engineering Geographic Information Systems CIVE 7397 Spring 09

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

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

4. File-based Data Models
Geographic coordinates and attributes
are stored in separate but linked files
Arc
Info
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 4

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

6. Storing Data - Cont’d 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 6

7. Geodatabase and Feature Dataset
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 7

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
Object Class
Relationship
Workspace 9

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

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

13. Relationship
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 13

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

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

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. Geographic Coordinate
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