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D'Spain, GL, Terrill E, Chadwell CD, Smith JA, Lynch SD.  2006.  Active control of passive acoustic fields: Passive synthetic aperture/Doppler beamforming with data from an autonomous vehicle. Journal of the Acoustical Society of America. 120:3635-3654.   10.1121/1.2346177   AbstractWebsite

The maneuverability of autonomous underwater vehicles (AUVs) equipped with hull-mounted arrays provides the opportunity to actively modify received acoustic fields to optimize extraction of information. This paper uses ocean acoustic data collected by an AUV-mounted two-dimensional hydrophone array, with overall dimension one-tenth wavelength at 200-500 Hz, to demonstrate aspects of this control through vehicle motion. Source localization is performed using Doppler shifts measured at a set of receiver velocities by both single elements and a physical array. Results show that a source in the presence of a 10-dB higher-level interferer having exactly the same frequency content (as measured by a stationary receiver) is properly localized and that white-noise-constrained adaptive beamforming applied to the physical aperture data in combination with Doppler bearnforming provides greater spatial resolution than physical-aperture-alone bearnforming and significantly lower sidelobes than single element Doppler beamforming. A new broadband beamformer that adjusts for variations in vehicle velocity on a sample by sample basis is demonstrated with data collected during a high-acceleration maneuver. The importance of including the cost of energy expenditure in determining optimal vehicle motion is demonstrated through simulation, further illustrating how the vehicle characteristics are an integral part of the signal/array processing structure. (c) 2006 Acoustical Society of America.

DeSanto, JB, Sandwell DT, Chadwell CD.  2016.  Seafloor geodesy from repeated sidescan sonar surveys. Journal of Geophysical Research-Solid Earth. 121:4800-4813.   10.1002/2016jb013025   AbstractWebsite

Accurate seafloor geodetic methods are critical to the study of marine natural hazards such as megathrust earthquakes, landslides, and volcanoes. We propose digital image correlation of repeated shipboard sidescan sonar surveys as a measurement of seafloor deformation. We test this method using multibeam surveys collected in two locales: 2500m deep lightly sedimented seafloor on the flank of a spreading ridge and 4300m deep heavily sedimented seafloor far from any plate boundary. Correlation of these surveys are able to recover synthetic displacements in the across-track (range) direction accurate to within 1m and in the along-track (azimuth) direction accurate to within 1-10m. We attribute these accuracies to the inherent resolution of sidescan data being better in the range dimension than the azimuth dimension. These measurements are primarily limited by the accuracy of the ship navigation. Dual-frequency GPS units are accurate to approximate to 10cm, but single-frequency GPS units drift on the order of 1m/h and are insufficient for geodetic application.