Terrain referenced navigation--woods data base model

Claim 1

A terrain referenced navigation system for use in an aircraft comprising: (a) a means for determining a current terrain elevation from the aircraft having a current terrain elevation output; (b) a means for inertial navigation having a latitude/longitude positional output, a selected position update input and a selected velocity update input; (c) a means for storing a digital terrain elevation map having a terrain latitude/longitude input connected to the latitude/longitude positional output and having a digital terrain elevation residual output and a woods indicator output and a digital terrain elevation output wherein the means for storing a digital terrain elevation map provides the digital terrain elevation residual output, woods indicator output, and digital terrain elevation output in response to the terrain latitude/longitude input, and wherein the woods indicator output indicates the existence or absence of a deciduous forest in the terrain; (d) a means for generating a woods state adjustment to the digital terrain elevation output so as to provide a woods adjusted digital terrain elevation output in accordance with the present season when said deciduous forest is indicated, the woods state adjustment means being coupled to the woods indicator output and the digital terrain elevation output; (e) a means for computing the difference between elevations connected to the current terrain elevation output and the woods adjusted digital terrain elevation output, wherein the means for computing the difference between elevations also includes a terrain error output; and (f) a means for terrain correlation connected to the digital terrain elevation residual output and the terrain error output and wherein the means for terrain correlation provides a terrain velocity update and a terrain position update.