Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular Vision
Spherical buoys serve as water surface markers, and their location information can help unmanned surface vessels (USVs) identify navigation channel boundaries, avoid dangerous areas, and improve navigation accuracy. However, due to the presence of disturbances such as reflections, water obstruction,...
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MDPI AG
2025-04-01
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| Series: | Journal of Marine Science and Engineering |
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| Online Access: | https://www.mdpi.com/2077-1312/13/4/733 |
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| author | Shiwen Wu Jianhua Wang Xiang Zheng Xianqiang Zeng Gongxing Wu |
| author_facet | Shiwen Wu Jianhua Wang Xiang Zheng Xianqiang Zeng Gongxing Wu |
| author_sort | Shiwen Wu |
| collection | DOAJ |
| description | Spherical buoys serve as water surface markers, and their location information can help unmanned surface vessels (USVs) identify navigation channel boundaries, avoid dangerous areas, and improve navigation accuracy. However, due to the presence of disturbances such as reflections, water obstruction, and changes in illumination for spherical buoys on the water surface, using binocular vision for positioning encounters difficulties in matching. To address this, this paper proposes a monocular vision-based localization method for spherical buoys using elliptical fitting. First, the edges of the spherical buoy are extracted through image preprocessing. Then, to address the issue of pseudo-edge points introduced by reflections that reduce the accuracy of elliptical fitting, a multi-step method for eliminating pseudo-edge points is proposed. This effectively filters out pseudo-edge points and obtains accurate elliptical parameters. Finally, based on these elliptical parameters, a monocular vision ranging model is established to solve the relative position between the USV and the buoy. The USV’s position from satellite observation is then fused with the relative position calculated using the method proposed in this paper to estimate the coordinates of the buoy in the geodetic coordinate system. Simulation experiments analyzed the impact of pixel noise, camera height, focal length, and rotation angle on localization accuracy. The results show that within a range of 40 m in width and 80 m in length, the coordinates calculated by this method have an average absolute error of less than 1.2 m; field experiments on actual ships show that the average absolute error remains stable within 2.57 m. This method addresses the positioning issues caused by disturbances such as reflections, water obstruction, and changes in illumination, achieving a positioning accuracy comparable to that of general satellite positioning. |
| format | Article |
| id | doaj-art-86f0eba2c483412c9b7448d8331d09a9 |
| institution | DOAJ |
| issn | 2077-1312 |
| language | English |
| publishDate | 2025-04-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Journal of Marine Science and Engineering |
| spelling | doaj-art-86f0eba2c483412c9b7448d8331d09a92025-08-20T03:13:58ZengMDPI AGJournal of Marine Science and Engineering2077-13122025-04-0113473310.3390/jmse13040733Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular VisionShiwen Wu0Jianhua Wang1Xiang Zheng2Xianqiang Zeng3Gongxing Wu4Key Laboratory of Transport Industry of Marine Technology and Control Engineering, Shanghai Maritime University, Shanghai 201306, ChinaKey Laboratory of Transport Industry of Marine Technology and Control Engineering, Shanghai Maritime University, Shanghai 201306, ChinaKey Laboratory of Transport Industry of Marine Technology and Control Engineering, Shanghai Maritime University, Shanghai 201306, ChinaShanghai Auto Subsea Vehicles Inc., Shanghai 201306, ChinaKey Laboratory of Transport Industry of Marine Technology and Control Engineering, Shanghai Maritime University, Shanghai 201306, ChinaSpherical buoys serve as water surface markers, and their location information can help unmanned surface vessels (USVs) identify navigation channel boundaries, avoid dangerous areas, and improve navigation accuracy. However, due to the presence of disturbances such as reflections, water obstruction, and changes in illumination for spherical buoys on the water surface, using binocular vision for positioning encounters difficulties in matching. To address this, this paper proposes a monocular vision-based localization method for spherical buoys using elliptical fitting. First, the edges of the spherical buoy are extracted through image preprocessing. Then, to address the issue of pseudo-edge points introduced by reflections that reduce the accuracy of elliptical fitting, a multi-step method for eliminating pseudo-edge points is proposed. This effectively filters out pseudo-edge points and obtains accurate elliptical parameters. Finally, based on these elliptical parameters, a monocular vision ranging model is established to solve the relative position between the USV and the buoy. The USV’s position from satellite observation is then fused with the relative position calculated using the method proposed in this paper to estimate the coordinates of the buoy in the geodetic coordinate system. Simulation experiments analyzed the impact of pixel noise, camera height, focal length, and rotation angle on localization accuracy. The results show that within a range of 40 m in width and 80 m in length, the coordinates calculated by this method have an average absolute error of less than 1.2 m; field experiments on actual ships show that the average absolute error remains stable within 2.57 m. This method addresses the positioning issues caused by disturbances such as reflections, water obstruction, and changes in illumination, achieving a positioning accuracy comparable to that of general satellite positioning.https://www.mdpi.com/2077-1312/13/4/733spherical buoysUSVellipse fittingmonocular visionlocalization |
| spellingShingle | Shiwen Wu Jianhua Wang Xiang Zheng Xianqiang Zeng Gongxing Wu Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular Vision Journal of Marine Science and Engineering spherical buoys USV ellipse fitting monocular vision localization |
| title | Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular Vision |
| title_full | Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular Vision |
| title_fullStr | Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular Vision |
| title_full_unstemmed | Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular Vision |
| title_short | Water Surface Spherical Buoy Localization Based on Ellipse Fitting Using Monocular Vision |
| title_sort | water surface spherical buoy localization based on ellipse fitting using monocular vision |
| topic | spherical buoys USV ellipse fitting monocular vision localization |
| url | https://www.mdpi.com/2077-1312/13/4/733 |
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