Generally, the need for geometric operations on images arises from the fact that we want to relate the pixel coordinates to the world coordinates. This is required to be able to measure the position, size, distance, and other geometric parameters of the imaged objects. In Sections 4.3.1 and 4.3.2, the chain of transformations from world coordinates via camera coordinates and image coordinates to pixel coordinates was discussed. Section 4.3.2f introduced the simplest geometric distortion — radial distortion — as one of the basic seven third-order lens aberrations. These sections set the stage for which kind of geometric operations are required.