A Combined Ray Tracing Method for Improving the Precision of the USBL Positioning System in Smart Ocean

Abstract

The ultra-short baseline positioning system (USBL) has the advantages of flexible application and easy installation, and it plays an extremely important role in the underwater positioning and communication. The error of the USBL in underwater positioning is mainly caused by a ranging error due to ray tracing, a phase difference error of the USBL, and acoustic noise in the underwater communication. Most of these errors are related to the changes in the sound speed during its propagation through the ocean. Therefore, when using the USBL for underwater detection, it is necessary to correct the sound speed profile in the detection area and optimize the ray tracing. Taking into account the actual conditions, this paper aims at correcting the model of underwater sound speed propagation and improving the tracking method of sound lines when the marine environment in the shallow sea area changes. This paper proposes a combined ray tracing method that can adaptively determine whether to use the constant sound speed ray tracing method or the equal gradient ray tracing method. The theoretical analysis and simulation results show that the proposed method can effectively reduce the error of slant distance in USBL compared with the traditional acoustic tracking method and the constant sound speed ray tracing method. The proposed sound ray correction algorithm solves the contradiction between the number of iterations and the reduction of positioning error and has engineering application value.

An Ultra-Short Baseline Underwater Positioning System with Kalman Filtering

“…They proposed various types of array element types [ 1 , 2 , 15 , 16 , 17 , 18 ]. Many positioning methods also have been presented to improve the positioning accuracy [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 19 , 20 , 21 , 22 , 23 , 24 ].…”

“…When the marine environment changed in the shallow sea area, the propagation speed model needed to be corrected. The authors in [ 5 ] proposed a combined ray-tracing method to determine whether to use the constant acoustic speed ray-tracing method or the equal gradient ray-tracing method. References [ 6 , 7 ] considered the installation error and multi-path error during underwater positioning and proposed calibration and reduction methods to enhance the positioning method.…”

“…According to the baseline length of the acoustic positioning system, the positioning systems can be classified traditionally into three types [1][2][3]: the long baseline (LBL) positioning system, the short baseline (SBL) positioning system, and the ultra-short baseline (USBL) positioning system. Relative to the other two types, the USBL possesses the advantages of its simplicity, efficiency, and accuracy [5][6][7]. However, due to the negative impact of some uncertain factors [1,[4][5][6][7], including multi-path propagation of acoustic signals, environmental interference, and installation error during the positioning procedure, these uncertain factors lead to poor positioning results, which cannot meet the requirements of many applications, or even worse, it may provide a wrong reference value for the latter processing methods.…”

“…Relative to the other two types, the USBL possesses the advantages of its simplicity, efficiency, and accuracy [5][6][7]. However, due to the negative impact of some uncertain factors [1,[4][5][6][7], including multi-path propagation of acoustic signals, environmental interference, and installation error during the positioning procedure, these uncertain factors lead to poor positioning results, which cannot meet the requirements of many applications, or even worse, it may provide a wrong reference value for the latter processing methods. To improve the positioning accuracy, many researchers and scholars presented numerous works [1,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23].…”

“…To improve the positioning accuracy, many researchers and scholars presented numerous works [1,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. The authors in [2][3][4][5][6][7][8][9] analyzed the errors and faults during underwater positioning; it took measurements to restrain the error. The authors in [1,10,11] utilized filters or multiple interacting models to improve the positioning accuracy.…”