### ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

## 4pSP6. Estimation of spatial backscatter power spectra from sonar images.

**Jules S. Jaffe
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*Marine Physical Lab., Scripps Inst. of Oceanogr., La Jolla, CA 92093
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Two- and three-dimensional power spectral estimation from sonar backscatter
images is an important area of research that has ramifications for understanding
the underlying structure of many environmental features. In one case, that of
backscatter from groups of animals, the interanimal correlation distances are
the inverse Fourier transform of the three-dimensional power spectrum.
Estimation of three-dimensional power spectra from sonar data is made difficult
because of the spreading of the sonar beams as a function of range which results
in a lower resolution image. In multidimensional signal processing parlance, the
resulting collected sonar data have been convolved with a spatially variant
kernel. Standard signal processing methods have difficulty when applied to these
kinds of functions, as the usual assumption is that the data have been obtained
from a spatially invariant kernel. A method is proposed to estimate the power
spectrum of such images by first starting with an ensemble. It is shown how the
spatially variant problem can then be converted into a spatially invariant
problem. Straightforward methods for power spectral estimation are then used to
determine the spectrum. Examples of the use of the methodology on
three-dimensional sonar data will be used to illustrate the method.