using lossless float data like GeoTIFF files is a good idea. The two grids can be recreated by using a program in Fortran and source data from NGA. "Test versions" of EGM2008 include PGM2004, 2006, and 2007.

As with all spherical harmonic models, EGM2008 can be truncated to have fewer coefficients with lower resolution.

EGM2020

EGM2020 is to be a new release (still not released as of July 2025) with the same structure as EGM2008, but with improved accuracy by incorporating newer data. It was originally planned to be

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