Impact of the horizontal gradient of sound speed on seafloor geodetic positioning

doi:10.11947/j.AGCS.2024.20230551

Abstract

Abstract:

The complex and dynamic marine environment results in a sound speed structure characterized by distinct vertical stratification. Additionally, influenced by oceanographic processes such as warm currents and internal waves, the sound speed field exhibits significant horizontal gradients, which are critical factors affecting high-precision underwater positioning. In this paper, the impact of horizontal gradients in the sound speed field on underwater positioning is investigated based on a three-dimensional ray-tracing positioning model, and the definition of the average gradient of the sound speed field and its inversion model are presented. Then the main factors influencing the accuracy of horizontal gradient inversion are further analyzed. The results indicate that positioning errors are closely related to the direction of the horizontal gradient, the location of seafloor transponders, and the size of the surface trajectory network. When the magnitude of the horizontal gradient reaches 10^-5 (m/s/m), it can lead to positioning errors exceeding decimeter level in deep sea environments at depths of 3000 m. The seafloor positioning model considering the horizontal gradient parameters of the sound speed field can significantly enhance positioning accuracy. Moreover, the estimation of the horizontal gradient parameter in the average sense can achieve centimeter-level precision positioning.

Key words: horizontal gradient, underwater positioning, 3D acoustic ray tracing, average gradient, positioning error, parameter inversion

CLC Number:

P258

Jie ZHOU, Shuqiang XUE, Zhen XIAO, Ying XU, Kaiming WANG, Jingsen LI. Impact of the horizontal gradient of sound speed on seafloor geodetic positioning[J]. Acta Geodaetica et Cartographica Sinica, 2024, 53(12): 2328-2337.

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参数种类	参数配置
海面网半径/m
海底控制网半径/m	1500
海底点深度/m	3000
观测时长/min	80
观测历元	1200
水平格网间隔/m	200
垂直格网间隔/m	100
参考声速剖面间隔/m	100
水平梯度方向	N方向
其他误差	无

海底点	坐标真值			解算策略	定位误差
海底点	E	N	U	解算策略	ΔE	ΔN	ΔU
M01	0	0	-3000	Model1	-0.001 0	0.217 5	-0.000 5
				Model2	-0.001 6	-0.001 1	0.003 3
				Model3	0.000 5	0.008 6	-0.000 2
M02	1 060.660 2	1 060.660 2	-3000	Model1	-0.012 7	0.210 2	0.063 5
				Model2	-0.005 1	-0.002 7	0.001 6
				Model3	0.012 1	0.022 7	-0.037 3
M03	-1 060.660 2	-1 060.660 2	-3000	Model1	-0.012 8	0.211 2	-0.064 0
				Model2	0.000 2	0.001 9	0.004 9
				Model3	0.012 1	0.022 7	0.037 0
M04	1 060.660 2	-1 060.660 2	-3000	Model1	0.011 0	0.210 0	-0.064 3
				Model2	-0.005 1	0.001 1	0.003 7
				Model3	-0.011 1	0.022 9	0.038 2
M05	-1 060.660 2	1 060.660 2	-3000	Model1	0.010 4	0.211 0	0.064 2
				Model2	-0.000 1	0.006 0	0.002 6
				Model3	-0.011 6	0.022 6	-0.038 5

方向	仿真平均梯度	模型3估计
E方向	0	-2.481 1×10^-7
N方向	2.15×10^-5	3.230 2×10^-5

海底点	Model1定位误差			Model3定位误差
海底点	ΔE	ΔN	ΔU	ΔE	ΔN	ΔU
M01	-0.034 4	0.089 1	0.267 2	0.001 7	0.007 5	-0.004 4
M02	-0.131 5	-0.004 5	0.256 3	0.002 2	0.013 1	-0.010 8
M03	0.055 1	0.188 4	0.228 2	0.004 3	0.008 1	0.001 6
M04	-0.121 2	0.179 9	0.215 8	0.008 8	0.004 8	0.003 1
M05	0.061 0	-0.003 2	0.274 3	-0.006 5	0.013 6	-0.007 0

参数名称	参数设置
B样条阶数	3
B样条节点间隔	k_t：15 min
B样条节点间隔	k_e、k_n：15、15 min
B样条平滑因子	k_t：1
B样条平滑因子	k_e、k_n：1、1