Optimal method for USBL underwater acoustic positioning by combining TDOA and TOA

In this paper we present an optimal method for Ultrashort Baseline (USBL) underwater acoustic positioning by combining Time Difference of Arrival (TDOA) and Time of Arrival (TOA). For the estimation of the bearing angles, on the basis of Least Squares (LS) method and Maximum Likelihood (ML) method, the Regularized Least Squares (RLS) method is designed based on the optimization criterion. LS and ML methods are optimal estimation method in a certain criterion, but the accuracy of LS method is relatively low, and ML method requires relatively strict conditions, although the accuracy of ML method can be a theoretical upper bound. RLS method is designed using nonlinear least squares, which overcomes the drawbacks of ML method. After a lot of simulation validation, the performance of RLS method is much better than LS method, very close to ML method. RLS method has a good resistance to the measurement error of TDOA, even if the measurement error of TDOA is very big, it can also have an ideal location precision.