1. A system for automatically registering a sensed image with a reference image, the system comprising: a sensor, supported on a platform, that acquires an image of a scene and which provides at least one sensor parameter that indicates a perspective of the sensor relative to the scene; a reference image database; a digital elevation database; at least one processing subsystem that: determines a footprint of the sensor relative to a coordinate system associated with the reference image database and the digital elevation database; accesses the digital elevation database to obtain a reference digital elevation model geocoded in the coordinate system and whose geographic extent encompasses an area that includes the sensor footprint; accesses the reference image database to obtain a reference image geocoded in the coordinate system and that encompasses an area that includes the sensor footprint; generates a synthetic 3-D model of an area around a center of the scene by combining the geocoded reference digital elevation model and the geocoded reference image such that each pixel of the geocoded reference image is associated with an elevation from the geocoded reference digital elevation model; transforms the synthetic 3-D model into a synthetic perspective image, with the transforming being based on a type of the sensor and the at least one sensor parameter; and registers the sensor image of the scene with the synthetic perspective image to geocode the sensor image using a mutual information model.