Synthetic aperture radar (SAR) images obtained in real time on a moving vehicle can provide a means for obtaining fix data for the vehicle navigation system. Reference features are located in the SAR images through the use of map matching techniques, with each match providing a measurement of range and range rate to a known reference point. Three matches or fixes made in different directions can provide data for a complete position and velocity determination. A map matching technique has been developed for use with SAR images that utilizes a reference tem-plate that encodes only the shape (and not the difficult-to-predict image intensity levels) of the selected reference feature. Through an adaptive and localized normalization of the sensed image pixel amplitudes a matching metric is computed that is a strong function of the degree of shape match of the sensed image and the reference template but is only weakly dependent on the image intensity and contrast. This results in the reference feature being acquired and located with high probability even in the presence of competing features with possibly higher contrast. The map matching algorithm is described and results of theoretical analysis of its performance charac-teristics are presented with specific attention given to the effects of scene scintillation or speckle in the sensed imagery. The algorithm has been used on a large data base of SAR imagery with good success. Several examples are included to indicate typical performance for both urban and rural environments.
Edwin R. Hiller,
"Map-Matching Technique For Synthetic Aperture Radar Images", Proc. SPIE 0186, Digital Processing of Aerial Images, (4 September 1979); doi: 10.1117/12.957505; https://doi.org/10.1117/12.957505