Advances in Doppler-based navigation of underwater robotic vehicles

New low-cost commercially available bottom-lock Doppler sonars can augment or replace the acoustic time-of-flight navigation systems commonly employed for three-dimensional underwater robot vehicle navigation. The paper first reviews conventional techniques for underwater vehicle navigation, and describes a Doppler-based navigation system developed by the authors. Second, we identify principal limitations to the bottom-track precision of Doppler based navigation systems. Third, we analyze the effect of heading-sensor errors on Doppler bottom-track precision. Experimental results compare bottom-track error resulting from a Doppler navigation using low-precision magnetic heading sensor with bottom-track error resulting from a high-precision a ring-laser gyroscope. The experiments were conducted during a field deployment in which the new robot navigation system enabled precision acoustic and optical survey as well as minimally invasive object recovery from hydrothermal vents in the Guaymas Basin, Gulf of California at 27/spl deg/N 111.5/spl deg/W, at 2000 m depth.