Statistical Ocean-Acoustics and Environmental Inversion after Stochastic Propagation and Scattering
Abstract
LONG-TERM GOAL The long term goal of this research is to provide a unified statistical theory for ocean acoustic measurements made after stochastic propagation and scattering that includes procedures for quantitatively evaluating the performance of environmantal or target parameter estimates derived from these measurements. OBJECTIVES. (A) In recent years, a wide variety of acoustic techniques have been developed to probe the marine environment. These techniques typically require the nonlinear inversion of acoustic field data measured on a hydrophone array. The data, however, are often randomized by the addition of naturally occurring ambient noise or by fluctuations in the waveguide's refractive index and boundaries. The nonlinear inversion of random data often leads to estimates with biases and variances that are difficult to quantify analytically. It has become popular in recent years to (1) simply assume that biases are negligible and to (2) compute limiting bounds on the variance of these nonlinear estimators, since these bounds are usually much easier to obtain than the actual variance. A major problem, however, is that the estimators may be strongly biased and that the bounds are only guaranteed to converge to the true variance of the estimator under sufficiently high signal-to-noise ratio (SNR). One of the primary objectives of this year s research is to apply higher order asymptotic theory to derive general expressions for the 1st-order-bias and 2nd-order-variance of a general maximum likelihood estimate and to apply these expressions in a variety of ocean acoustic inverse problems, such as matched field processing, matched field inversion and active sonar range estimate.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1999
- Accession Number
- ADA630251
Entities
People
- Nicholas C. Makris
Organizations
- Massachusetts Institute of Technology