Trimble GGF

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GGF_INFO describes the metadata included in the .GGF file header (146 bytes)

Data is stored as 4byte LE floats, the only known exception is OSU91.GGF (2byte integer format, probably some bit is set in the flags)

ORIGIN: top left
0 0 TNL GRID FILE\0 XXX\0*
1 0 TNL GRID FILE
0x30 8-> ymin (°) (Min Latitude in decimal degrees)
0x38 8-> ymax (°) (Max Latitude in decimal degrees)
0x40 8-> xmin (°) (Min Longitude in decimal degrees)
0x48 8-> xmax (°) (Max Longitude in decimal degrees)
0x50 8-> dy (°)    (Step size for latitudes, in decimal degrees)
0x58 8-> dx (°)  (Step size for longitudes, in decimal degrees)
0x60 4->  (vNY, nrows)
0x64 4->  (vNX, ncols)
       North Pole
       South Pole
       Missing Value (nodata)
       Scale
       Flags*
0x92+ data*