The Key Technology Research On Ships’ Celestial Navigation Based On Star Pattern Recognition

It is very complicated for naval ships to fix positions with astronavigation. Toensure naval ships can acquire accurate position information by astronavigation starpattern recognition， the author in this paper researches some key technologicalmethods in naval ships by astronavigation， which includes the building of stardatabase by radian value of Delaunay triangulation， star recognition based onapproximate matching of vertex subdivision radian set， elimination of clouds in seaand sky images on the basis of reactive Agent of levels and fast detection algorithm ofline between sea and sky according to improved Hough transform. Results ofexperiments and analysis show that methods mentioned above can be used to fixpositions precisely by astronavigation information on naval ships，and then to correctchronic navigation errors by position information. This dissertation will do thefollowings：Present paper research position switch relation in all kinds of coordinatedsystems， and time system and conversion relation in different time systems. And wereveal elaborately characteristic set of subdivision radian between stars is set up inlight of the known standard star database. By screening out fixed stars over7.0fromSAO Star Catalog， we build characteristic recognition star database of Delaunaytriangulation.Star recognition method and exact probability reliability method of it areproposed. First， we need to denoise and recover star image that we get， and extractevery star point by a new method of approximate marginal division， and then doDelaunay triangulation to every star point. We are based on star recognition method ofapproximate matching approach of of vertex subdivision radian set to find that pair offixed stars most similar to characteristic set in star database. Finally， we put forwardan analysis method of star recognition reliability that can test and recognize exactprobability， judge recognition correctness of the star points which have beenrecognized.The attitude judgement of naval ships is vital to fix position. Rake angle of linesbetween sea and sky shot by infrared viewfinder on the bow and starboard is used tojudge rolling angle and course angle of the ship. Reactive Agent of levels is firstapplied to remove clouds in image of sea and sky efficiently and precisely. And thenwe， according to improved Hough transform， use fast detection algorithm of linebetween sea and sky to calculate lean value of the ship.Present paper compare drift errors between Celestial Navigation proposed in thisdissertation and chronic navigation system. First，we analyze and simulate errors thatchronic navigation system makes. Secondly， we exert importance on researching theerror factors， such as atmospheric refraction error， image pixel error， which thisCelestial Navigation approach makes. Thirdly， we reveal the error range made bythis astronavigation approach，and this range is smaller than the one made by chronicnavigation system. Finally， we demonstrate formulations of calculating longitudeand altitude by right ascension and declination of zenith.Present paper use that set of methods proposed in this dissertation to simulate system. There are a sum of recognition data and calculation process when we acquireand recognize a new star image and judge recognition reliability of star image.Combining attitude of the ship， we can get real position of zenith in the star image.Finally， we can calculate longitude and altitude of the ship in the light of world time.By analyzing systematic simulation experiment， we can find that the method ofusing arc set fuzzy identification is very successful because its rate of success canreach98%. At the same time， judgement of rake angle of ships is correct and valid.Therefore， the method of using Celestial Navigation to locate places and directionson ships is reliable and valid.