Geometry of a spherical image
Warren M. Krueger · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1993
A notion of spherical image is described that serves as a basis for defining the various geometric edges in a uniform way, for distinguishing between different views of an object, and for recovering range. The notion proposed here augments the point set image with a tangent vector frame field which arises naturally from the gradient of range and the perspective projection process.