Assume all images are presented on a D × D grid L, also centered at the
origin, with D ∼ 300. Thus the reference grid is a small subset of the image
grid. Henceforth y will denote locations on the reference grid and x will denote
locations in the scene or image. A pose of the object in the image is determined
by a location xc and a map A ∈ A, where A is some subset of linear (and perhaps
even non-linear) transformations of the plane. Typically A accommodates a range