Performs an overlay of points on areas.
The Group By parameter specifies a series of attributes that must match on the point and polygon features before the attributes will be merged. This can be used to ensure that the overlay occurs only on certain groups of features.
Note: How parallel processing works with FME: see About Parallel Processing for detailed information.
This parameter determines whether or not the transformer should perform the work across parallel processes. If it is enabled, a process will be launched for each group specified by the Group By parameter.
Parallel Processing Levels
For example, on a quad-core machine, minimal parallelism will result in two simultaneous FME processes. Extreme parallelism on an 8-core machine would result in 16 simultaneous processes.
You can experiment with this feature and view the information in the Windows Task Manager and the Workbench Log window.
No: This is the default behavior. Processing will only occur in this transformer once all input is present.
By Group: This transformer will process input groups in order. Changes on the value of the Group By parameter on the input stream will trigger batch processing on the currently accumulating group. This will improve overall speed if groups are large/complex, but could cause undesired behavior if input groups are not truly ordered.
The Overlap Count Attribute added to output area features holds the number of point features that they contained.
If Areas First is set to Yes, then the PointOnAreaOverlayer assumes that all Area features will enter the transformer before any Point features. This can reduce memory use of the PointOnAreaOverlayer if you have many Point features to overlay. Any further Area features that arrive after the first Point feature will be logged with a warning and discarded.
If attributes on the incoming and original feature share the same name, but are not geometry attributes that start with fme_, then they are deemed conflicted.
Merge Incoming: The original feature will retain all of its own un-conflicted attributes, and will additionally acquire any un-conflicted attributes that the incoming feature has. This mode will handle conflicted attributes based on the Conflict Resolution parameter.
Prefix Incoming: The original feature will retain all of its own attributes. In addition, the original will acquire attributes reflecting the incoming feature’s attributes, with the name prefixed with the Prefix parameter.
Only Use Incoming: The original feature will have all of its attributes removed, except geometry attributes that start with fme_. Then, all of the attributes from one (arbitrary) incoming feature will be placed onto the original.
Use Original: If a conflict occurs, the original values will be maintained.
Use Incoming: If a conflict occurs, the values of the incoming will be transferred onto the original.
If the Accumulation Mode parameter is set to Prefix Incoming, this value will prefix attributes that are being added to the original feature from the incoming feature.
If the optional List Name is supplied, the attributes of each area containing an output point are added to that point's list, and the attributes of each point contained by an output area are added to that area's list.
Note: List attributes are not accessible from the output schema in Workbench unless they are first processed using a transformer that operates on them, such as ListExploder or ListConcatenator. All list attribute transformers are displayed in the Contents pane of the Transformer Help under Lists. Alternatively, AttributeExposer can be used.
- Each point receives the attributes of the area(s) it is contained in, and each containing area receives the attributes of each point it contains.
- Note that intersections between area features are not computed.
- If a point falls exactly on the line between polygons, FME always include points on the boundary as being in. So if a point is on the boundary of two polygons, it will be called "in".
- If you have a lot of features to process, you can improve overlay performance by also using the Clipper transformer. The Clipper also provides different options for a point that falls exactly on a line. See the Clipper example from the FME Knowledge Center for information on how to use less memory using the Clippers First parameter.
- If you have a lot of Point features in particular, you can reduce memory usage of the PointOnAreaOverlayer by using the Areas First parameter.
- Aggregates are not supported by this transformer.
- Note that where Point geometries are expected as input, PointCloud geometries are not supported.
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.
FME Licensing Level
FME Professional edition and above
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Search for samples and information about this transformer on the FME Knowledge Center.