Investigation on underwater positioning stochastic model based on acoustic ray incidence angle

High-precision underwater positioning requires more accurate stochastic model. The commonly used equal weight stochastic model (EWSM) cannot be effective in precise underwater positioning process under the assumption of equal-precision observation. In this paper, inaccurate stochastic model effect on the positioning precision is analyzed and a novel acoustic ray incidence angle stochastic model (IASM) is proposed by taking the ranging error and the uncorrected acoustic ray bending error into consideration to improve positioning accuracy. The performance of both EWSM and IASM involving four different forms (the general proportional form, the cosine form, the exponent form and the piecewise cosine form) is tested by the simulation and experiment. The simulation results show that positioning accuracy for underwater static objects is 0.386 m when adopting EWSM while positioning accuracy is 0.334 m, 0.196 m, 0.318 m and 0.091 m when adopting four forms of IASM respectively and sequentially. The experiment results show that the positioning accuracy can be superiorly improved from 1.187 m in EWSM scheme to 0.991 m based on IASM in piecewise cosine form. It's obvious that the novel IASM can perform better than conventional EWSM in terms of positioning accuracy according to testing results.