https://pubs.usgs.gov/of/2004/1258/Data/grid_facts.txt
The magnetic and gravity grids are available in the following formats:
1. Geosoft OasisMontaj (*.grd, *.grd.gi) binary format
2. Grid Exchange Format (.gxf) (an ascii grid transfer format)
3. ESRI Spatial Analyst (.flt, .hdr) binary format
Hi @shahsamkit,
FME can read the Esri Spatial Analyst binary format, using the Esri .hdr Raw Raster reader. However, the .hdr files supplied with the data seem to be missing a few entries required by the reader to define the data type.
If you add the following entries to the Ascii .hdr file, the data will read correctly:
pixeltype float
nbits 32