555 
3. FUTURE DEVELOPMENT--VENUS RADAR MAPPER 
For the Venus Radar Mapper (VRM) mission, the Photogrammetry Section of the 
Branch of Astrogeology, U. S. Geological Survey, at Flagstaff, AZ, has been 
continuing to conduct research and development in mapping, using side- 
looking radar images. Because of the unique radar geometry, mainly 
effected by its method of illumination and image formation, topographic 
contour maps cannot be directly compiled on conventional stero- 
photogrammetric equipment. Various approaches have been attempted and 
experiments have been performed (Wu, 1979, Wu et.al., 1980). One approach 
interfaces the existing radar steroplotter to a Modcomp computer so that 
ground coordinates can be determined by measuring radar image coordinates 
through stereoscopic viewing. Interface hardware is completed and software 
development is in progress. Since the studies of stereo radar-mapping 
problems emphasize geometric correction and have advanced to a point where 
the radar layover problem can be mathematically solved (Wu, 1983), the | 
current approach is to modify the existing software used for map 
compilation from panoramic photography on the analytical stereoplotter, 
which also has a line-scan geometry. Once the layover distortion is 
corrected, the stereo model should be retained on the plotter. Stereo 
radar compilation will then be performed using practically the same 
procedures, i.e., interior, relative, and absolute orientations that are 
used in conventional photogrammetry. Future development of stero radar 
compilation will probably involve automatic image correlation. 
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