Sea bottom line tracking in side-scan sonar image through the combination of points density clustering and chains seekin
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ORIGINAL ARTICLE
Sea bottom line tracking in side‑scan sonar image through the combination of points density clustering and chains seeking Aixue Wang1,2,3 · Ian Church2 · Jun Gou4 · Jianhu Zhao1,3 Received: 2 April 2019 / Accepted: 13 October 2019 © The Japan Society of Naval Architects and Ocean Engineers (JASNAOE) 2019
Abstract Sea bottom line is the echo boundary between the water column and seabed on side-scan sonar waterfall image. Tracking it correctly is the basis for geometric and radiative correction of side-scan sonar image. Because of the interfering echoes under complex water environment, the sea bottom line cannot be tracked through traditional threshold and smoothing algorithms. Therefore, a new method, taking full advantage of the spatial distribution characteristics of the sea bottom line, is proposed, in which points density clustering and chains seeking are the two core processes. The former clustering process can be regarded as a filter to cluster points along a direction that is approximately parallel to the track line,and the points are grouped to chains if they are density reachable in a searching neighborhood. Then, by adopting the five principles and tracking strategy given in this paper, the chains relevant to the sea bottom line are sought and identified to finish the tracking work. The test results show that the proposed method performs well even in a complex water environment and has better stability and anti-interference ability compared with traditional tracking methods. This research improves the side-scan sonar data processing, and makes it more accurate, automatic and intelligent. Keywords Side-scan sonar · Sea bottom line tracking · DBSCAN clustering · Chains distinguishing
1 Introduction The side-scan sonar system is a cost-effective tool for acquiring high-resolution geomorphic images of the seabed and is frequently used for underwater exploration and other maritime surveying. Its obvious design characteristics are towing operation and slant range imaging mode, but it has its own disadvantage that the location of towfish cannot be precisely estimated and a water column blank is produced in the center of the waterfall image [1]. Because of lacking * Aixue Wang [email protected] 1
School of Geodesy and Geomatics, Wuhan University, 129 Luoyu Road, Wuhan, China
2
Department of Geodesy and Geomatics, University of New Brunswick, 15 Dineen Drive, Fredericton, Canada
3
Institution of Ocean Science and Technology, Wuhan University, 129 Luoyu Road, Wuhan, China
4
Guangzhou Marine Geological Survey, 188 Guanghai Road, Guangzhou, China
intuitive location information, it is difficult to read waterfall image; so it can only be used for exploring underwater target qualitative judgment other than precision measurement. Generating a side-scan sonar image with intuitive coordinates requires a series of postprocessing [2]. To achieve the image, the most primary and difficult working is searching the water column region on both sides to track the sea bottom line [3]. As i
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