Performs an area-on-area overlay (intersection of polygons) so that all input areas are intersected against each other and resultant area features are created and output. The resultant areas can accumulate attribute from any overlapping polygons.

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Typical Uses

  • Deconstructing overlapping polygons to produce the intersections and differences
  • Comparing multiple datasets for area overlaps
  • Performing area calculations based on overlapping area data

How does it work?

The AreaOnAreaOverlayer takes in area features. All polygons are considered against each other, and where they overlap, new polygons are created that represent both the overlapping area and the original areas with the overlap removed.

The new polygons can retain attributes from all original relevant features (performing a spatial join), and a count of the number of overlaps encountered during the overlay. This count starts at 1 for all features, as they are considered to overlap themselves.

Aggregates can either be deaggregated before processing or rejected.


Usage Notes

Choosing a Spatial Transformer

Many transformers can assess spatial relationships and perform spatial joins - analyzing topology, merging attributes, and sometimes modifying geometry. Generally, choosing the one that is most specific to the task you need to accomplish will provide the optimal performance results. If there is more than one way to do it (which is frequently the case), time spent on performance testing alternate methods may be worthwhile.

To correctly analyze spatial relationships, all features should be in the same coordinate system. The Reprojector may be useful for reprojecting features within the workspace.


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



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