Research On Marine Celestial Navigation Based On Fisheye Camera

Celestial navigation is an important means of autonomous navigation technology, by analyzing its research status, development trends, and current problems, this paper proposes a new marine celestial navigation method which utilizes a fisheye camera to image the stars and horizontal line simultaneously. This paper studies the principles, processes, and all technical aspects of marine celestial navigation based on fisheye camera, including star image acquisition, star point extraction, horizontal line extraction, horizontal line fitting, star identification, and celestial navigation algorithm. Marine celestial navigation experiments were performed based on the theoretical method, and the results indicated that it takes about two minutes when using 10 images to realize celestial navigation, the mean positioning error is about 0.5 nautical miles, the mean course error is about 18 arcseconds. While traditional celestial navigation method based on the sextant relies on manual measurements, and could only be adopted during the twilight to achieve ship positioning accuracy of 2~5 nautical miles by observing 20~30 minutes, which illustrates that marine celestial navigation based on fish-eye camera has achieved a significant breakthrough in terms of efficiency, accuracy, degree of automation and availability. The main research content and innovations are as follows:(1)To address the problems of traditional marine celestial navigation, such as relay on traditional manual measurement, low accuracy, limited observation period and other issues, a new method which utilizing a fisheye camera to image the stars and horizontal line simultaneously was proposed. Experimental results indicated that this method can realize automated marine celestial navigation, its navigation efficiency and accuracy were increased by more than 10 times and 4 times respectively, and available observation periods can be expanded from twilight to the entire night.(2)Celestial navigation requires precise horizontal datum. When providing ship attitude parameters by inertial platform problems come out such as complicated device and difficult integration. when utilizing the gradienter to determine the horizontal datum problems come out such as low precision, slow response, difficult calibration, and when using sextant observing horizontal line to determine the horizontal datum relies on manual measurement. In view of the above problems, this paper proposed a new method using the fisheye camera to image the horizontal line, and then fitting horizontal line to determine the horizontal datum, which do not require external device, and could achieve accuracy of up to 37.2 arcseconds.(3)A star identification method of shipboard fisheye camera was proposed, which include initial mode and tracking mode. The initial mode could realize star identification in the absence of prior information such as unknown ship position or navigation lock- lose, and could achieved 98% of correct rate. The tracking mode could realize rapid and accurate star identification in the process of ship sailing.(4)The multi-star celestial positioning algorithm was studied in depth. Firstly, basic principles of the multi-star celestial positioning model was deduced, secondly, in view of systematic errors is exist in celestial elevation angle observations, a multi- level equal altitude celestial positioning algorithm was proposed, and finally to solve the problem of outliers and the large error in the observations, a robust celestial positioning algorithm was proposed, numerical examples indicated that the celestial positioning accuracy could be increased by 2~3 times.(5)The marine celestial navigation algorithm was studied in depth, a unified model of multi-star positioning and orientation was established firstly, which could solve vessel’s position and cross at the same time, and then the vessel’s motion model and the observation model based on fisheye camera were established, finally adopts robust adaptive filtering was used to determine the vessel’s position, course and speed according to the two models.