Doppler sonar applied to precision underwater navigation

Doppler sonars have been used for many years to aid underwater navigational systems, reducing their complexity and enhancing their accuracy. This paper describes recent improvements that significantly advance Doppler performance. A new, state-of-the-art, phased array transducer has been developed which offers a number of significant operational advantages. Among these improvements, the phased array eliminates speed of sound dependency, a principle error source in older designs. The conformal surface of the array also eliminates turbulence and simplifies array mounting. Performance advances have also been achieved by the use of digital signal processing (DSP) techniques. Adaptive bandwidth tracking filters and the use of a maximal likelihood digital spectral estimator, have greatly improved available accuracy. Recent advances in manufacturing techniques have made a miniaturized system optimized for autonomous underwater vehicle (AUV) practical