FME Transformers: 2024.1

Categories
Data Quality
Geometries
Related Transformers
AreaOnAreaOverlayer
Snapper

AreaGapAndOverlapCleaner

Repairs area topologies by resolving gaps and overlaps between adjacent areas.

Jump to Configuration

Typical Uses

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

How does it work?

The AreaGapAndOverlapCleaner receives features with valid area geometry and cleans up shared boundaries by dissolving overlaps and filling in gaps between polygons.

Input aggregate geometry may be either deaggregated or rejected.

Z values and measures are supported.

Repairing Overlaps and Gaps

Overlaps and gaps are processed slightly differently.

Both use the Tolerance and Repair Method parameters to determine how they are resolved. Gaps are further handled according to the Fill All Gaps parameter.

Overlaps are all processed, all the time. If the overlap is within the Tolerance distance, the repair is done automatically. If the overlap is greater than the tolerance, the Repair Method choice is used.

Gaps within the Tolerance distance are repaired automatically. If Fill All Gaps is Yes, gaps greater than the tolerance are repaired according to the Repair Method choice. If Fill All Gaps is No, they are not repaired.

 

Fill All Gaps

Within Tolerance

Greater Than Tolerance

Overlaps

 

Automatic

Per Repair Method

Gaps

No

Automatic

Untouched

Gaps

Yes

Automatic

Per Repair Method

Tolerance

Tolerance is a distance in the ground units of the features’ coordinate system. The choices are to enter a value or choose Automatic.

For most transformers with a Tolerance parameter, Automatic is recommended, but it is frequently not the correct choice here. Automatic will calculate a value that accounts for minute differences introduced by binary limitations, rounding errors, and the like (See Geometry Concepts > Tolerance). The calculated value is written to the log file.

Tolerance is always greater than zero.

Tolerance > Automatic does not consider the size of gaps and overlaps present in the data. For many use cases, this value is too small and an explicit value should be entered. The value should be guided by the nature of the input geometry (size of gaps and polygons) and whether you want the repairs to be automatically handled or determined by a specific Repair Method.

Repair Method

Gaps and overlaps greater than the Tolerance value are repaired according to the Repair Method:

  • Longest Boundary: Gaps and overlaps are allocated to the area with the longest boundary.
  • Random: Gaps and overlaps are allocated to areas selected at random.
  • Priority (Edge Preserving): Gaps and overlaps are allocated according to a numeric priority attribute:
    • Overlaps go to the higher priority area.
    • Gaps go to the lower priority area.
    • The boundary of the higher priority area is preserved.
  • Priority (Area Enlarging): Gaps and overlaps are allocated according to a numeric priority attribute:
    • Both overlaps and gaps go to the higher priority area.
    • The higher priority area may be enlarged.

When using Priority methods, zero (0) is the highest priority. If there is a conflict where more than one area has the same priority, one is selected arbitrarily.

Examples

Usage Notes

  • When unexpected results are output, it can often be corrected by adjusting the Tolerance value.
  • To repair only overlaps (not gaps), consider using a Dissolver.
  • Invalid area geometry such as self-intersecting or degenerate polygons will not be rejected, but will not be repaired properly.
  • Donut holes are gaps, and may be processed accordingly.

Creating and Modifying Area Features

These transformers work with polygons in a variety of ways.

Configuration

Input Ports

Output Ports

Parameters

Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

For more information, see Transformer Parameter Menu Options.

Reference

Processing Behavior

Group-Based

Feature Holding

Yes

Dependencies  
Aliases SliverRemover
History  

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, Open Government Licence - British Columbia, and/or Open Government Licence – Canada.