GNSS/Sonar Track Line Layout On The Sea Surface And Research On Its Influence On Seafloor Positioning

The seafloor geodetic network is an extension of the terrestrial geodetic network and is one of the infrastructures for the construction of national geodetic datum.The Global Navigation Satellite System-Acoustics(GNSS-A)ranging combined seafloor geodetic technique is the key technology to achieve the precise positioning of seafloor datum points,and the accuracy of underwater positioning mainly depends on the geometric configuration of the control network and the accuracy of acoustic ranging.Therefore,the optimal design of control network in underwater positioning has important reference significance for improving the positioning accuracy of datum points.In addition,the complex dynamic change of marine environment is the thorny error source to restrict the underwater positioning accuracy.This paper focuses on the optimization of GNSS-A control network at sea surface and the modeling of sound speed field error compensation,and the main research contents and innovations include:(1)The principle and positioning model of active sonar localization are discussed,and on this basis,the construction of GNSS-A simulation algorithm is carried out,the two-round travelling time pursuit algorithm for simulating the active acoustic observation is proposed,and the sound velocity field modeling method with periodic function is constructed in the context of the empirical orthogonal function to achieve the active acoustic observation and the marine environmental error simulation of underwater positioning.(2)The applicability of the two types of acoustic positioning models,sound velocity profile correction and propagation time correction,to weaken the system error is compared and analyzed.The experimental results show that under the simulated water depth of 3000 meters,the time variation of the sound speed field can cause decimeter-level positioning errors.Both methods have effective compensation effects for sound velocity reference errors and can reduce positioning errors to centimeter-level.Moreover,optimizing the sea surface track line configuration helps to weaken the impact of reference sound velocity errors.(3)Considering the characteristics of the vertical change of the measured sound velocity,the double exponential vertical variation sound velocity profile correction method and the B-spline vertical variation sound velocity profile correction method are proposed,and the open source measurement observation data is used for positioning calculation.The experimental results show that although the inversion profile sound velocity has vertical sound velocity changes,and the sound velocity changes at the same depth have volatility,the two positioning methods and the sound velocity profile correction method only have differences of less than a centimeter in positioning results.Therefore,it is believed that the positioning results are independent of the vertical variation of the profile.