F. Parallax 

1. StereoPhoto Geometry

The basic geometry of an overlapping photo pair is shown in Figure F-1. Each point in the overlap area appears on both photographs. They appear in different locations on both photos; this is what allows us to see the image in 3D.

Figure F-1 StereoPhoto Geometry

Except for stricly photo interpretation, we would also like to use the geometry to determing a point's numeric lcation. To do that, we need to undertand and use parallax.