Multiple Geometries

A multiple geometry is a collection containing parts that are interpreted to be independent geometries. Each part is treated as its own complete geometry, separate from other parts.

For example, a multiple geometry may contain two parts, one named Area containing an area representation of a feature, and one named Point which contains a point representation of the same feature.

Multiple geometries are a different concept from multi geometries, such as MultiPoint and others.

Multiple geometries are often successfully handled in the same way aggregate geometries are handled, even though they are conceptually slightly different than aggregates.

MultipleGeometrySetter and MultipleGeometryFilter are two transformers that are helpful to use with multiple geometries in a workspace. Several database formats support reading and writing of multiple geometries.

Multiple Geometry Attributes

• fme_geometry = fme_aggregate
• fme_type = fme_collection

Coordinate Systems and Multiple Geometries

To preserve the coordinate system of multiple geometry features when writing to a database format, with each geometry in its own column, you must set the Spatial Reference System Identifier (SRID) of the coordinate system as a trait on each of the multiple geometries. Use the following transformers, in order, for each geometry:

1. CoordinateSystemExtractor to retrieve the coordinate system name as attribute Coordsys (change from the default _coordsys).
2. GeometryPropertySetter to set attribute Coordsys as a trait. (Specify Property to Set: Traits from Attributes and Source Attributes: Coordsys.)
3. MultipleGeometrySetter to aggregate the geometries.