Anti-midlines with inner method enhance positioning accuracy in navigation by three celestial-bodies

The paper based on spherical triangle theory and double celestial-bodies positioning principle, in the model of various astronomical positioning calculate formula, makes analysis for algorithm and its error aim to traditional using of celestial observations height calculating ship´s positioning. Put forward an astronomical positioning solution of the Anti-midline method combined with inner method to achieve three celestial-bodies positioning. Since the preparation of computer programs and databases with a horoscope, it not only saves time to get rid of the steps of cumbersome look-up table, computing and mapping, but also improves the positioning accuracy theoretically, so that driving ship drivers from the cumbersome out of balance, there is more time and effort taken to ensure the safety of navigation.