ASA 125th Meeting Ottawa 1993 May

3aUW3. Microbathymetry from shape from shading of sidescan acoustic imagery.

Clyde Nishimura

Christian de

Naval Res. Lab., Code 7420, 4555 Overlook Blvd., Washington, DC 20375-5350

Shape from shading (SFS) is a methodology for extracting the topography of a surface given the acoustic (or electromagnetic) backscattered imagery. As a sidescan image is of generally finer spatial resolution than multibeam bathymetry at the same frequency, there is some promise that SFS can provide information on the microtopography of an area. However, several key assumptions need to be made in order to apply SFS techniques on sidescan data; foremost of these assumptions is that of homogeneity of the backscattering properties of the seafloor across the imaged area. The sidescan sonar device can also introduce ambiguities in the SFS method if a flat-bottom assumption is used to position the pixels and/or the far-field transmit beam pattern is poorly known. The results obtained from SFS can be readily compared to acoustic data collected from new bathymetric sidescan systems that produce coregistered bathymetry and sidescan images (companion presentation by C. de Moustier, same session). [Work supported by ONR.]