The OpenCities Map Topology Ribbon Group provides tools to cleanup and create valid topology from lines, points, and boundaries. In addition, the Edit / Modify ribbon group contains Merge Polygons and Split Polygons which assist in topology creation.
In certain instances, polygons will contain holes that should be subtracted from the enclosed area. For polygon plus the hole to be processed properly, the Allow Holes preference must be enabled. This setting is available in the User or Personal Preferences dialog in the Topology category:
If the setting is not enabled, the enclosing polygon will cover the hole and the hole’s area will not be taken into consideration.
Allow Holes enabled
Allow Holes not enabled
The Map Topology workflow opens the Topology Tools Group on the OpenCities Map Ribbon
For more information and instructions for using the Topology Commands, see the Topology Operations chapter in the OpenCities Map Help document.