### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 2aAO5. Optimizing shallow-water sound-speed estimation using parameter
resolution bounds.

**Nicholas C. Makris
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*Naval Res. Lab., Washington D.C. 20375
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A technique is under development to optimize experimental design for
estimation of 3-D sound-speed structure by inversion of acoustic data. The
motivation is to take advantage of a priori knowledge of invariant
environmental parameters to estimate the minimum number of sensors necessary
and their optimal deployment geometry for a well constrained inversion. First,
static environmental information, such as bathymetry, geoacoustic parameters of
the sediment, and mean sound-speed structure of the water column, is input to
an appropriate range-dependent acoustic model for a given sensor deployment
geometry. Next, a theoretical lower bound on estimation error for the
water-column sound-speed structure is obtained via the Cramer--Rao bound. The
deployment geometry is then perturbed until the estimation error is within
acceptable bounds for oceanographic and acoustic modeling. However, the choice
of sound-speed parametrization can also severely affect the accuracy of an
inversion. For example, an empirical orthogonal function (EOF) representation
typically has higher resolution for fewer parameters than a discrete cell
representation. But this is at the cost of more limiting assumptions. These
issues are addressed by computing the theoretical lower bound on estimation
error for discrete cell, EOF, and Fourier internal wave representations of 3-D
sound-speed structure.