On the Longitude and Latitude in Japan as derived from Observations of the Moon

Abstract

If there be an error in the co-ordinates of an observing site, in the meaning of geo centric geometry, the position of a celestial body at a finite distance as observed from such a site may be proved to be affected by the error, when compared with the correct geo centric position of the body. The present paper deals with the inverse problem of this effect and shows that such errors can be deduced from a series of astronomical observa tions, meridisan transits of the Moon and occultation observations, as compared with the corresponding series of standard observations.
By this method the author obtained the corrections to the adopted values of the longitude and latitude of the Japanese datum point as follows:
Δλ=-21″.5+5″.4 Δψ= +12″.6±2″.6.
These corrections can reduce the geodetic system of Japan to the “geocentric-geometrical” system. These corrections, together with a correction, da= +0.59+0.37 km recently obtained by the author, to the value of the equatorial radius of Bessel's spheroid, which is adopted in Japan, seems to be able to explain the famous “gap” between the triangulation nets of the Manchurian system and those of the Korean system, found in their boundary area. From the residuals in the explanation, one can suspect that a further correction in azimuth, ΔA= +5″, should exist in the Korean triangulation system as a whole, which might likely have raised in the course of extension to the said boundary area from the Tsushima. (The Editor).