This paper examines the problem of registering a recon-naissance side-looking synthetic aperture radar (SAR) image to a three-dimensional reference map. The registration technique developed in the present work is based on computing an image-to-data base correspondence in terms of a SAR sensor model as a function of such parameters as altitude, range, scale, etc. If their exact values are known, the model can precisely predict the two-dimensional image coordinates for any three-dimensional data base point, thereby accomplishing registration. However, the platform ephemeris data usually provide only model parameter estimates. The objective, then, is to improve them so that the model can predict the image location of any data base point within a desired accuracy range. Preliminary investigations demonstrate the feasibility of achieving location accuracy within 50 m.