How FME Manages Grid Shift Files
Grid shift files are used when reprojecting between coordinate systems that have different datums.
FME supports conversions between coordinate systems using different datums. Many datum transformations are not mathematically definable and require the use of grid of shifts. If you attempt to make a datum transformation of this kind without the appropriate grid shift file in place, FME will abort the translation.
The FME installation includes a configuration file for managing the use and location of grid shift files.
These files are found in the Reproject folder in the FME installation folder. For example, the file Nad27ToNad83.gdc includes file paths to both the Canadian and US grid shift files for the NAD27 <-> NAD83 transformations.