Patent US 4,017,985

From stored environmental digital data giving coordinates of terrain features such as ridges and valleys and their associated brightness and color there is selected data on features lying in a vertical plane extending from a center which is the ground position of an elevated viewpoint. By data-processing means, the terrain elevation profile and the color profile for the vertical plane are generated. These profiles are then converted to a radar intensity profile by incrementing a ground sweep or to a perspective color profile by incrementing the view angle sweep. The process is repeated for each next adjacent sector until the entire desired azimuth range is covered. Presentation means is swept vertically, reproducing stored terrain profile patterns, with successive vertical sweeps lying side by side. Using equal angle increments for successive azimuth angles gives perspective representation for a spherical display. Equal successive increments in tangent of the angle give exact perspective for a flat display such as a TV monitor. By including radar reflectivity in environmental data store, simulated radar PPI display is obtainable from same store, using somewhat similar sweep techniques. Visual and radar simulations may be placed to be viewed side by side, for training in comparison of radar return with visual scene of same terrain.