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Tip: It is easier to manipulate the contents of these files through Tools > Options > Coordinate Systems. |
Geodetic Data Catalog files are configuration files used by the coordinate subsystem in FME to perform datum shifts when grid files holding position-related shift deltas are required (such as NAD 27 to NAD 83).
These files, which have a .gdc extension, are located in the <fme install directory>/Reproject/ directory, and you can open them with any text editor. They typically contain the locations of the grid files that will be used by the datum shift algorithms, and may additionally contain information about the nature of the grid shift algorithm employed.