Epipolar navigation is the optoelectronic counterpart of human spatial perception.
Epipolar navigation works by evaluating the way an image changes as viewed from a moving perspective. Suppose that you are piloting an aircraft over the ocean. The only land in sight is a small island. The on-board computer sees an image of the island that constantly changes shape. Above figure shows three sample sighting positions (A, B, C) and the size/shape of the island as seen by a machine vision system in each case. The computer has the map data, so it knows the true size, shape, and location of the island. The computer compares the shape and size of the image it sees at each point in time, from the vantage point of the aircraft, with the actual shape and size of the island from the map data. From this, the computer can ascertain the altitude of the aircraft, its speed and direction of movement relative to the surface, its latitude, and its longitude.