海洋内波对海底精密定位的影响

Effect of ocean internal waves on high-precision seafloor geodetic positioning

全球导航卫星系统-声呐组合观测技术通常基于具有固定结构的声速剖面实施;由于海洋密度分层导致的内波会导致海洋声速场时空变化。本文探讨了海洋声速误差对水下定位的影响,仿真不同内波影响条件下的四维时空声速场变化,在此基础上,分别研究了具有固定声速结构的静态声速剖面时,海洋内波对水下定位的影响和采用估计海洋声速梯度的水下定位模型时,海洋内波引起的海洋声速时空变化参数估计问题,验证了该模型可以提取海洋内波影响。研究表明:海底定位精度与内波的振幅、频率、波长等紧密有关,且定位误差主要来源于大尺度低频内波,而小尺度、高频内波更多表现为随机误差从而影响观测精度;而水平梯度刻画极为复杂,单船载观测难以实现,需要进行多载体联合观测。

Global navigation satellite system-acoustic(GNSS-A)underwater positioning usually adopts a sound speed profile with fixed structures to observe.However,the ocean sound speed field constantly changes with ocean temperature,salinity,and pressure,particularly the ocean internal waves caused by ocean density stratification,which further exacerbate the spatiotemporal changes in the ocean sound speed field.This paper first discusses the effect of ocean sound speed error on underwater positioning and then simulates the spatiotemporal variation in a four-dimensional sound speed field under different internal wave effect conditions.On this basis,GNSS-A simula-tions are conducted to separately investigate the effect of ocean internal waves on underwater positioning by adopting a static sound speed profile with a fixed structure for positioning and the estimation of the spatiotemporal parameter variation in ocean sound speed due to ocean internal waves by adopting the underwater positioning model consider-ing the gradient of ocean sound speed.The model′s ability to extract the effect of ocean internal waves is verified.The research shows that seafloor positioning accuracy is closely related to the amplitude,frequency,and wavelength of internal waves.The positioning error mainly comes from the large-scale low-frequency internal waves,while the small-scale and high-frequency internal waves present more random errors,which affect the observation accuracy.The horizontal gradient characterization is very complicated and difficult to achieve by single-ship observation,thus necessitating multi-vector joint observation.