Accurate registration of optical satellite imagery with elevation models for topographic correction

It is necessary to remove the effects of topography from optical satellite imagery if automated techniques are to be used to infer surface properties. This is especially the case in mountainous terrain where variable slope normals cause variation in both illumination and reflectance of light. Digital elevation models (DEMs) are required to model slope normals and make topographic corrections. However, it is difficult to achieve accurate registration between ortho-rectified satellite images and DEMs. We show how this mis-registration, which can be spatially variable, may be accounted for with the use of a local correlation filter. The filter determines the offset between a DEM shade map and ortho-rectified satellite image for every pixel. Association of satellite image pixels with the 'correct' slope normal in topographic correction removes the majority of ghosting and high-frequency artefacts.