COMPUTATION PROGRAMS OF THE ASTRONOMICAL VESSEL POSITION

Abstract

In open sea sailing, as opposed to sailing with satellite navigation systems, the astronomical vessel position (AVP) is not limited by military codes. If programs can be developed to solve the AVP directly, drawbacks of current methods for performing marine operations can be greatly improved. Complete AVP computations have two necessary points: compute the observed altitude and compute the AVP for two bodies. Thus, this paper utilizes Matlab ® programming language to develop the observed altitude (ObsAltPro) and the AVP by using intercept method (IMPro-2) programs, respectively. Adopting the ObsAltPro can avoid the use of nautical almanacs and directly obtain the observed altitudes of various celestial bodies between 1986 and 2050. As for merits of using the IMPro-2, they can skip limits of tabular methods and directly use the dead reckoning (DR) as the input variable to replace the assumed position (AP). To address the deficiencies of the intercept method (IM), iteration computation is added into the latter program as a verification function. The above two programs, through demonstrated examples, have shown advantages of being simple, fast, and accurate.