A first Gray code technique and a second raster calibration technique can be combined to create a precise mapping between pixel locations of the camera and pixel locations of the projector(s). In one aspect the technique of using the raster calibration images is eliminated by interpolating the projector coordinate information decoded from the Gray code images. In another aspect camera images are processed to reduce errors caused by noise so that text can be displayed without any noticeable misalignment between projectors. In a third aspect, a scale factor is calculated based on the relative height/width of projector regions in the captured calibration images. Calibration images are recalculated using the scale factor to provide greater correspondence between the mapping of a low resolution camera to the high-resolution projectors.