In GIS, topology refers to the rules and spatial relationships that define how geographic features interact with one another. In ArcGIS Pro, topology allows users to implement integrity rules that ensure geospatial data meets standards of accuracy and consistency. These rules may include constraints such as preventing overlapping polygons or improper line intersections.
Establishing proper topology is essential for maintaining high-quality geospatial data. Common topological issues may include segmented lines, disconnected features, overextended lines, and improper intersections in line features. For polygon features, typical errors include gaps or overlaps between polygons.
Major topological errors in a layer of lines and polygons.
This tutorial demonstrates how to use feature classes from the geodatabase developed in the previous steps to identify and correct topological errors. While there are many types of topological issues that may occur in practice, the focus here is to show how ArcGIS Pro tools can automatically resolve the most common ones. Manual correction is often labor-intensive and can introduce human error, making automated solutions more reliable.
For additional information about topological rules, refer to the official online documentation available under “Geodatabase topology”.
Defining Topological Rules
Once the layers are included in the geodatabase, the next step is to define the topology. This involves setting rules that govern how features relate spatially. These rules help ensure that lines and polygons behave correctly, such as preventing overlaps or ensuring connectivity.
To resolve topological issues in the line layer, access the topology tools within ArcGIS Pro. Navigate to the “View” tab and select “Catalog View”. In the “City.gdb” geodatabase, locate the feature dataset named “C_ROAD_AXIS”. Right-click on it and choose “New > Topology”.
In the dialog window that appears, select the “ROAD_L” layer and proceed to define the appropriate topological rules. Complete the configuration by clicking “Finish”. The following rules are applicable to line features:
- Must Not Overlap (Line)
- Must Not Intersect (Line)
- Must Not Have Dangles (Line)
- Must Not Have Pseudo-Nodes (Line)
- Must Not Intersect Or Touch Interior (Line)
- Must Be Single Part (Line)
Definition of topological rules for the “ROAD_L” line layer.
To apply topology rules to the polygon layer “ZONES_PO” found in the geodatabase path “City.gdb > A_HUMAN_CONCENTRATION”, follow the same process to create a new topology. For polygon features, use rules that address the structural integrity of area features, such as:
- Must Not Have Gaps (Area)
- Must Not Overlap (Area)
Definition of topological rules for the “ZONES_PO” polygon layer.
