Vertical Grids

FME supports the following vertical grid formats:

  • Geoid96 (GEO)
  • Geoid99 (bin)
  • OSGM91 (txt)
  • Byn (byn)
  • Egm96 (grd)

The CsmapReprojector transformer can apply grids in any of these formats via a .gdc file, which is a text file that list one or more grid files in the formats listed above. Grids will be tried in order until one is found that provides coverage for the point being transformed. Grid files may be listed with absolute paths, or by paths relative to the .gdc file.

Example .gdc file contents for a grid file in the same folder as the .gdc:

# comments start with '#'

Some of the .gdc files shipped with FME reference grid files that are not included in the FME Form installer. You can download those grid files at