GeoDatabases

GeoDatabases implement an object-based GIS data model (the geodatabase data model). Each feature is stored in a row in a table that contains common features (lines, polygons, etc.). The vector shape of the feature is stored in the tables's shape field with feature attributes in other fields. this is probably what we want to use for our Archaeology project!

In addition, GeoDatabases can store raster images, data tables, and references to other tables. GeoDatabases can hold all your data in one location! They are like adding coverages, shapefiles and raster images into a DBMS.

Geodatabases can have build-in behavior; geodatabase features are completely stored in a single database; and large geodatabase feature classes can be stored seamlessly, not tiled.

Basic objects are:

• points
• lines
• areas
• multi-[point|line|area]

You can extend these by creating your own custom objects with custom behaviors. The following sections describe geodatabase specific types/behaviors described below.

Point Features

Network Junction Features are points that play a topological role in a network (somewhat like nodes in coverages) and come in two flavors: Simple and Complex.

• Simple junction features might be used to represent a fitting that connects two pipes. It could have validation behavior that would ensure that connected pipes are of the correct diameter and materials.
• Complex junction features plays a more complex role in a network and may for instance represent an electric switch that in position (a) connects A-B and in position (b) connects A-C

       B
       |
       |
 A --------- C

Line Features

Lines are built from three kinds of segments:

• Line segments (straight)
• circular arcs
• Bezier splines

Line features can have custom drawing behavior that generalizes the line depending on the map scale or that controls the placement of annotation along the line.

Network edge features features are Line features that play a topological role in a network. They can be used for tracing and flow analysis.

• A simple edge feature is a linear network feature that connects to junction features at its endpoints (Junction Features are described above). They can have connectivity rules. E.g. a 10 cm pipe must connect to a 10 cm fitting. They can also have special class methods, so a pipe feature could calculate the pressure drop of a liquid flowing from one end to another based on diameter, roughness and length. The can have special query, editing and data entry interfaces.

• A complex edge feature can support one or more junctions along its length and remain a single feature. Think of a power line (maybe even a single circuit in a house). Multiple lines may go from the main line at different places. Or you may have multiple plugs attached to a line. The can have special query, editing and data entry interfaces.

Polygon Features

Polygon features represent areas. The are formed from the line features described above. They must be closed shapes, but may have discontinuous parts such as separate islands. Polygons can also contain "islands" or "lakes".

Geodatabase objects are files that contain Personal Geodatabase FeatureDatasets. FeatureDatasets contain related objects