天測誤差の考察(日本航海学会第41回講演会)

抄録

The line of position by heaven body on the Mercator chart has some kinds of error. For example, there are 1. error due to the curveture of equall altitude circle 2. bearing error due to the difference between great circle bearing and Mercator bearing 3. distance (intercept) error due to the scale of Mercator chart. Usually they are so small that they are used to be negligible. But we have to understand the nature of these errors and we must know which error is bigger than other's. This paper gives a calculation some kinds of error in LOP on the Mercator and chart also some error tables. Another purpose of this paper is to investigate the formula, error due to curveture=tan (altitude)/6876. This formula gives a assumption that the equall altitude curve on the Mercator chart is a circle. This is not a circle and not a simple curve, as many bibliographies say. So this is not exact formula but approximate one. This paper gives the limit of its adaptation, exact and simple formula, some tables and digrams to obtain the error and so on.