How FME Identifies Coordinate Systems

These mapping file directives are used to identify the source and destination coordinate system:

<READER_KEYWORD>_COORDINATE_SYSTEM <coordinateSystemName>

<WRITER_KEYWORD>_COORDINATE_SYSTEM <coordinateSystemName>

If a coordinate system is specified in both the source format and the mapping file, the coordinate system in the mapping file is the one that will be used. The coordinate system specified in the source format is not used, and a warning is logged. If a source coordinate system is not specified in the mapping file and the format or system does not store coordinate system information, then the coordinate system is not set for the features that are read.

If a destination coordinate system is set and the feature has been tagged with a coordinate system, then a coordinate system conversion is performed to put the feature into the destination system. This happens after features leave the factory pipeline, but before they enter the transformation process.

If the destination coordinate system was not set, then the features are written out in their original coordinate system.

If a destination coordinate system is set, but the source coordinate system was not specified in the mapping file or stored in the source format, then no conversion is performed. The features are simply tagged with the output system name before being written to the output dataset.