A variation on the basic Mercator map projection based on the dynamics of satellite motion. The movements of the Landsat platform, sensors, and the Earth, expressed as functions of time, are used to calculate which latitudes and longitudes on the Earth correspond to locations in the projection plane. Thus, a continuous projection of the entire area of coverage is obtained. SOM is conformal and nearly totally distortion-free; it was developed by John Parr Snyder. See Universal Transverse Mercator.