太陽測観による船位測定について(I)(日本航海学会第17回講演会)

抄録

In the case of fixing noon position by observing heavenly bodies, the combination of ante-meridian (1st) and noon (2nd) Sights by the sun is most generally preferred. It is well-known that in this case, the best opportunity to take 1st sight varies with the combination of latitude and declination. However, we must bear in mind that the ship's position fixed by such a method is generally low in accuracy ; accordingly it is desirable to add past-meridian (3rd) sight to them, i.e. both of ante-meridian and noon sights to increase the accuracy of the day's standard noon position. In this paper, the writer studied about the most suitable opportunities to take 1st and 3rd sights according to various combinations of latitude and declination, and the accuracy of ship's positions by this method. Herewith, he tried to analyze them provided that these 1st and 3rd sights are preferred without restraint.