Source Localization in a Highly Variable Shallow Water Environment: Results from Ascot-01

Variability in the ocean environment can have a big impact on acoustic propagation. Acoustic receptions often contain multipath contributions with fluctuations that vary significantly from the direct path to the higher order multipath. Matched-field methods take advantage of the multipath to extract information about the source location and seabed properties. Matched-field processing is generally successful in environments that are not highly range dependent and do not vary significantly in time. However, in some cases the environmental conditions are too extreme for good propagation predictions and matched field results suffer. The ASCOT-01 acoustic experiments were conducted in June 2001 specifically to explore the limits of matched field methods in highly variable environments. Measurements were made over several days between a sound source and a moored vertical line array of receivers. Results characterizing the difficulties of matched field processing at this site will be presented. Source localization results using standard estimators will be compared with those using new alternatives intended to be robust against harsh environmental conditions.