Testing Topology with Topo Manager

Organisations often maintain themes such as cadastre/landbase, statistical and zoning themes by digitising each polygon but fail to ensure that the correct snapping is carried out.

The end result can be themes which show gaps and overlaps as shown opposite. Topology has been lost.

Internal Topology

Topo Manager's Testing routines can quickly analyze a single polygon theme for Internal Topology and identify a wide variety of types of topological errors.

  • Duplicate Polygons
  • Gaps and Overlaps
  • Dead Ends
  • Bowties, slithers and other sharp angles

Topo Manager can process 1800 parcels and report hundreds of errors in a few minutes.


  • 90.98% accuracy
  • GIS platform independence - Now supporting SQL Server 2008.
  • Powerful Reporting and QA tools

Vertical Topology

Testing for Vertical Topology between themes is supported with the Spatial Difference routine.

Topo Manager's Testing routines can quickly compare a zoning layer with base cadastre/landbase and report links not found in the cadastre. These unmatched links can come from lines not properly snaped to the underlying themes or from valid lines joining features. An example of this would a zoning layer based on the cadastre where the boundary crosses the road reserve. Another example is where a statistical boundary is based on road, rail and river centreline and on the cadastre, and the polygons cross between the various layers, e.g. from the road to the river centreline.


Topo Manager's sophisticated routines realign a statistical boundary to road, rail and cadastre.

Here, a simple point theme shows the beginning and ends of many slithers, whilst other polygon themes show gaps and overlaps.

Ease of use

  • Just a single scripting line produces a variety of Shape files identifying all identifiable errors
  • Allows the incumbent GIS to be used to do any manual edits that might be needed
  • Allows comparison between original data and data processed by Topo Clean and Topo Snap.