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Search Results (3)

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Keywords = bottom bounce path

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24 pages, 26274 KiB  
Article
Imaging Seafloor Features Using Multipath Arrival Structures
by Zhaohua Su, Jie Zhuo and Chao Sun
Remote Sens. 2024, 16(14), 2586; https://doi.org/10.3390/rs16142586 - 14 Jul 2024
Viewed by 1312
Abstract
In this paper, we propose an imaging method for seafloor features based on multipath arrival structures. The bistatic sonar system employed consists of a vertical transmitting array and a horizontal towed array. The conventional back projection (BP) method, which considers the direct path [...] Read more.
In this paper, we propose an imaging method for seafloor features based on multipath arrival structures. The bistatic sonar system employed consists of a vertical transmitting array and a horizontal towed array. The conventional back projection (BP) method, which considers the direct path from the source to the seafloor scatterer and then to the receiver, is used in this system. However, discrepancies between the calculated delay values and the actual propagation delay result in projection deviations and offsets in the seafloor features within sound intensity images. To address this issue, we analyze the multipath structures from the source to the scatterer and then to the receiver based on ray theory. The delay at each grid is calculated using different multipaths, considering the distances from the seafloor grids to the source and the receiver. In the direct zone, the delay is determined using the direct ray and the surface reflection ray, while in the bottom bounce area, the delay is calculated using the bottom–surface reflection ray and the surface–bottom–surface reflection ray. Numerical simulations and experimental results demonstrate that the proposed method rectifies the delay calculation issues inherent in the conventional method. This adjustment enhances the accuracy of the projection, thereby improving the imaging quality of seafloor features. Full article
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20 pages, 5518 KiB  
Article
TMA from Cosines of Conical Angles Acquired by a Towed Array
by Antoine Lebon, Annie-Claude Perez, Claude Jauffret and Dann Laneuville
Sensors 2021, 21(14), 4797; https://doi.org/10.3390/s21144797 - 14 Jul 2021
Cited by 6 | Viewed by 2651
Abstract
This paper deals with the estimation of the trajectory of a target in constant velocity motion at an unknown constant depth, from measurements of conical angles supplied by a linear array. Sound emitted by the target does not necessarily navigate along a direct [...] Read more.
This paper deals with the estimation of the trajectory of a target in constant velocity motion at an unknown constant depth, from measurements of conical angles supplied by a linear array. Sound emitted by the target does not necessarily navigate along a direct path toward the antenna, but can bounce off the sea bottom and/or off the surface. Observability is thoroughly analyzed to identify the ghost targets before proposing an efficient way to estimate the trajectory of the target of interest and of the ghost targets when they exist. Full article
(This article belongs to the Special Issue Advances in Angle-Only Filtering and Tracking in Two and Three Dimensions)
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14 pages, 3912 KiB  
Article
Batch Processing through Particle Swarm Optimization for Target Motion Analysis with Bottom Bounce Underwater Acoustic Signals
by Raegeun Oh, Taek Lyul Song and Jee Woong Choi
Sensors 2020, 20(4), 1234; https://doi.org/10.3390/s20041234 - 24 Feb 2020
Cited by 10 | Viewed by 4463
Abstract
A target angular information in 3-dimensional space consists of an elevation angle and azimuth angle. Acoustic signals propagating along multiple paths in underwater environments usually have different elevation angles. Target motion analysis (TMA) uses the underwater acoustic signals received by a passive horizontal [...] Read more.
A target angular information in 3-dimensional space consists of an elevation angle and azimuth angle. Acoustic signals propagating along multiple paths in underwater environments usually have different elevation angles. Target motion analysis (TMA) uses the underwater acoustic signals received by a passive horizontal line array to track an underwater target. The target angle measured by the horizontal line array is, in fact, a conical angle that indicates the direction of the signal arriving at the line array sonar system. Accordingly, bottom bounce paths produce inaccurate target locations if they are interpreted as azimuth angles in the horizontal plane, as is commonly assumed in existing TMA technologies. Therefore, it is necessary to consider the effect of the conical angle on bearings-only TMA (BO-TMA). In this paper, a target conical angle causing angular ambiguity will be simulated using a ray tracing method in an underwater environment. A BO-TMA method using particle swarm optimization (PSO) is proposed for batch processing to solve the angular ambiguity problem. Full article
(This article belongs to the Special Issue Innovative Target Tracking Techniques for Modern Radar and Sonar Systems)
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