1. A method for generating a three dimensional edge model from two stereo pairs of images of an area of interest, the method comprising; in a three dimensional edge modeling engine: generating a first edge detected image from a first stereo image, the first edge detected image representing edges detected in the first stereo image; back projecting the first edge detected image into a first three dimensional edge model using a camera model associated with the first stereo image, the first three dimensional edge model being a volume of voxels in which each voxel has a probability, referred to as a voxel probability, that a given back projection of the first edge detected image intersecting a subject voxel is an edge; updating the voxel probabilities in the first three dimensional edge model with back projections of the first edge detected image; generating a second edge detected image from a second stereo image, the second edge detected image representing edges detected in the second stereo image; back projecting the second edge detected image into the first three dimensional edge model using a camera model associated with the second stereo image; stereo updating the voxel probabilities in the first three dimensional edge model with back projections of the second edge detected image; for a second stereo pair, repeating the foregoing resulting in a second three dimensional edge model; and merging the first three dimensional edge model and second three dimensional edge model resulting in a merged three dimensional edge model.