EGM96 (Earth Gravitational Model 1996)'s a geopotential model of the Earth consisting of spherical harmonic coefficients complete to degree and order 360. It's a composite solution, consisting of: (1) a combination solution to degree and order 70, (2) a block diagonal solution from degree 171 to 621, and (3) the quadrature solution at degree 360. This model's the result of a collaboration between the National Imagery and Mapping Agency (NIMA), the NASA Goddard Space Flight Center (GSFC), and Ohi… (More on Egm96)