Nonlinear Kalman filtering of long-baseline, short-baseline, GPS, and depth measurements

Moving ship tomography measures acoustic travel times between transmitters moored above the ocean floor and hydrophones on a cable tethered to a ship. The authors consider a Kalman filter that determines the location of a subarray of the hydrophones near the end of the cable. A long-baseline tracking system, consisting of floating buoys and the ship, acoustically measured the slant range to each hydrophone. The range to orbiting satellites was measured with the Global Positioning System (GPS). A short-baseline acoustic system measured range and direction from the ship to a beacon on the cable, and to each buoy. Depths at various points near the hydrophones were measured using three different pressure sensors. The Kalman filter combines these primary measurements and some supporting measurements to form an estimate of the buoy and hydrophone locations. An iterated correction step is used to adjust for the nonlinearities and an outlier detection scheme to make the filter robust