顾及声速结构时域变化的海底基准站高精度定位方法

Precise positioning method for seafloor geodetic stations based on the temporal variation of sound speed structure

目前广泛采用GNSS-A联合技术进行海底基准站定位,高精度位置反演通常基于声速剖面数据采用等梯度声线跟踪方法实现。但该方法使用的离散声速剖面忽略了声速结构的时域连续变化特性,制约海底点定位精度。本文顾及声速结构时域变化,引入三次B样条函数表征扰动声速,基于声线跟踪理论,构建“分步迭代-渐次修正”的位置信息和声速信息迭代反演模型,进行海底基准站坐标和扰动声速的渐次修正。采用南海实测数据进行验证,结果表明:传统不施加声速修正、基于二次多项式声速修正,以及基于三次B样条函数声速修正的方法,对应的观测值残差均方根误差分别为1.43、0.44和0.21 ms;施加声速修正的反演模型有效消除了声速结构变化引起的声速相关系统性误差,显著提高了海底基准站定位精度。

At present, GNSS-Acoustic(GNSS-A) combined technology is widely used in positioning for seafloor geodetic stations. Based on sound velocity profiles(SVPs) data, the equal gradient acoustic ray-tracing method is applied in high-precision position inversion.However, because of the discreteness of the SVPs used in the forementioned method, it ignores the continuous variation of sound velocity structure in time domain, which worsens the positioning accuracy. In this paper, the time-domain variation of sound speed structure(SSS) has been considered, and the cubic B-spline function is applied to characterize the perturbed sound velocity. Based on the ray-tracing theory, an inversion model of “stepwise iteration & progressive corrections” for both positioning and sound speed information is proposed, which conducts the gradual correction of seafloor geodetic station coordinates and disturbed sound velocity. The practical data were used to test the effectiveness of our method. The results show that the root mean square(RMS) errors of the residual values of the traditional methods without sound velocity correction, based on quadratic polynomial correction and based on cubic B-spline function correction are 1.43, 0.44 and 0.21 ms, respectively. The inversion model with sound velocity correction can effectively eliminate the systematic error caused by the change of SSS, and significantly improve the positioning accuracy of the seafloor geodetic stations.