Repairs area topologies by resolving gaps and overlaps between adjacent areas. An overlap occurs where two or more areas intersect each other, creating a region covered by multiple areas. A gap occurs where two or more areas fail to meet at a boundary.

Jump to Configuration

Typical Uses

  • Cleaning topology errors in a polygon coverage to create a single, continuous surface.

How does it work?

The AreaGapAndOverlapCleaner resolves the differences between adjacent areas, creating a topologically clean shared boundary by dissolving overlaps and filling in gaps between the polygons.

These operations are generally carried out within a specified Tolerance - the distance, in ground units - within which gaps are candidates for repair.

All processing within the Tolerance distance is automated. Processing outside of the Tolerance is performed according to the Repair Method parameter, which provides options for determining which polygons take precedence.

All overlaps are resolved, whether they fall within the tolerance or not. Gaps outside tolerance may optionally be resolved.

Tolerance may be set to any number zero (0) or greater, or calculated automatically. Setting Tolerance to zero will result in all overlaps and gaps being processed according to the Repair Method.

While all overlaps will always be processed, gaps outside the Tolerance will only be processed if the Fill All Gaps parameter is set to Yes.

Processing Behavior and Tolerance


Within Tolerance

Outside Tolerance

Overlaps Automatic According to Repair Method
Gaps Automatic Not processed
Gaps when Fill All Gaps = Yes Automatic According to Repair Method


Usage Notes

  • Requires valid area geometries. For example, self-intersecting, or degenerate areas will not be properly repaired.
  • If a single area is input, it will be output unchanged.
  • The AreaGapAndOverlapCleaner may create spikes when merging large overlaps to adjacent areas. However, spikes smaller than the tolerance will never be created. If these spikes are not desired, try increasing the tolerance.
  • Donut holes, if not filled by another area, are considered gaps in the coverage. They may be filled in if overlapped.


Input Ports

Output Ports


Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.


Processing Behavior


Feature Holding


Aliases SliverRemover

FME Community

The FME Community is the place for demos, how-tos, articles, FAQs, and more. Get answers to your questions, learn from other users, and suggest, vote, and comment on new features.

Search for all results about the AreaGapAndOverlapCleaner on the FME Community.


Examples may contain information licensed under the Open Government Licence – Vancouver and/or the Open Government Licence – Canada.