Research On Ship Astronomical Positioning Algorithm Based On Azimuth Angle

Astronomical positioning is an important autonomous positioning technology which uses natural celestial bodies as the navigation benchmark.Aiming at solving the problems existing in the current ship astronomical positioning technology,this paper proposes to use azimuth angle as the observation to determine the ship position by analyzing the development of astronomical positioning of ship at home and abroad,and based on astronomical positioning model of azimuthal method,the ship position can be directly obtained by numerical calculation method.The main research contents and innovations are as follows:(1)Traditional ship astronomical positioning of single celestial body needs to observe the different altitudes of the same celestial body at different time,and it also needs to determine the ship position by line moving method,this method is not immediacy and the method of altitude difference which be used to draw the ship’s position line is a straight line instead of a curve so that it can lead to errors.For solving this problem,this paper proposes a ship astronomical positioning algorithm that based on single celestial azimuth.This algorithm takes the altitude and azimuth angle of the single celestial body as observation,and can determine the ship position by numerical iteration.The model of ship astronomical positioning algorithm that based on single celestial azimuth is established.And then the model is verified and analyzed by celestial altitude and azimuth data: this algorithm does not require the drawing work of the ship line,and the solving process is simple,which can be used for fast and direct astronomical positioning of single celestial body.(2)Traditional ship astronomical positioning of two celestial bodies needs to observe the altitudes of two celestial bodies by observing the two celestial bodies and water-sky-line simultaneously,its positioning results and precision are often affected by the observation time of the water-sky-line.For solving this problem,this paper proposes a ship astronomical positioning algorithm that based on two celestial azimuths.This algorithm takes the two celestial azimuths as observation,and can determine the ship position by numerical iteration.The model of ship astronomical positioning algorithm that based on two celestial azimuths is established.And the model is verified and analyzed by celestial altitude and azimuth data: The result shows that this algorithm can avoid the tedious work of drawing the ship’s position line,and it does not need the observation of water-skyline.It can expand the use period of traditional ship’s astronomical positioning.(3)The pointer of traditional azimuth angle measuring instrument for celestial body usually can not point to the north pole accurately because of error accumulation or magnetic influence.This can affect the precision of the measurement of celestial body’s azimuth angle thus it will affect the precision of the azimuthal method of two celestial bodies for ship astronomical positioning.For solving this problem,this paper proposes a ship astronomical positioning algorithm that based on two celestial azimuths of three celestial bodies.This algorithm takes the two azimuths of three celestial bodies as observation,and can determine the ship position by numerical iteration.The model of ship astronomical positioning algorithm that based on two celestial azimuths of three bodies is established.And the model is verified and analyzed by celestial altitude and azimuth data: the method can eliminate the systematic error caused by the celestial azimuth measuring instrument without the ship line drawing and the water antenna observation.It can further improve the precision of ship astronomical positioning with the advantages of two celestial azimuthal method.