Geodatabase Topology Editing

Sherry FuCE697v

Final projectDec. 08, 2006

Basics of Topology Objects

• Creating a geodatabase topology – Cluster tolerance– Ranks– Topology rules

• Dirty areas• Validating a topology• Managing errors and exceptions

Topology in the Geodatabase• Spatial integrity of data

– Finds topology errors (user sets the rules)

– Fix with edit and topology tools• Coincidence based topology

– Snaps feature vertices– Single or multiple feature classes

• Feature topology is not stored– Only properties, errors, and exceptions are stored

Creating a Topology

• Topology properties– Participating feature classes– Cluster tolerance – Ranks – Topology rules

Cluster Tolerance

• Cluster tolerance should be very small• A distance within which all geometry is

considered coincident, or identical in location!• ArcGIS 9.2 : (1 cm / 100 cm in a meter) / 10 (1 cm / 100 cm in a meter) / 10

(order of magnitude) = 0.001(order of magnitude) = 0.001

Ranks

• Control how vertices move during validation

• Lower-ranked vertices move to higher-ranked vertices– Ranks: 1 (highest) to 50 (lowest)– Set ranks between feature classes

Topology Rules• Set as properties of the topology, 25 rules

available

– Between features on a single feature class – Between feature classes – Between subtypes

Validation

• Not Validated– Dirty areas exist

• Validated – Errors Exist– All dirty areas have been validated and errors

were found• Validated – No Errors

– All dirty areas have been validated and no errors were found

Dirty Areas

• Areas in the dataset that have not been validated– Entire extent is “dirty” when topology is first

created– May contain existing or undiscovered errors– Edits create dirty areas

Topology Editing Tools

• Validating a Topology• Topology Errors• Managing Errors

Overview

• Create a topology• Validate the topology• Examine topology errors• Perform edits to fix topology errors