A planar approximation for data compression of DRLMS data base is provided by General Electric. The data considered were the terrain elevation slope between adjacent points within a 1° X 1° rectangle. Because of the heterogeneity such a large area, smaller areas 1/1600 of the 1° X 1° rectangle were considered and the planar approximation applied to each of the smaller rectangles. To substantiate the need for a reduction of the 1° X 1° area, a roughness index for each of the 1600 blocks in the area in question was calculated.
The Grumman modification of the General Electric "Trig" (Triangle Generation) algorithm which implements this planar approximation reduces computational time and enhances the fidelity of the simulated video signal.