A process improves accuracy in mapping geodetic coordinates to image sensor coordinates via an image rational function. The image rational function is fitted to an image-to ground sensor model at an input grid of image u coordinates and image v coordinates, and further at geodetic longitudes, geodetic latitudes, and geodetic heights corresponding to the image u coordinates and the image v coordinates. This fitting generates fit residuals. The fit residuals are stored as a function of the image u coordinates, the image v coordinates, and the geodetic height coordinates. The fit residuals are applied to metadata associated with the image rational function. This application corrects for a residual error in a fit of the image rational function to the image-to-ground sensor model.