Latitude Service

the cooperation of scientific establishments to provide regular astronomical determination of the geographic latitudes of a number of points on the earth’s surface, specifically selected to study the motion of the geographic poles.

The International Latitude Service, later reorganized as the International Polar Motion Service, was created by a decision of the Twelfth International Geodetic Conference in 1898. Five latitude stations were established, located on the parallel 39° 08’ at approximately equal intervals by longitude; the stations began operations in 1899. Two of them were in the USA, one in Italy, one in Japan, and one in Russia, near the city of Chard-zhui (now Chardzhou, Turkmen SSR). Several stations were later established in the southern hemisphere. In 1919 the Chardzhui station was closed, and in its place the Ulug Beg International Latitude Station was established in the city of Kitab (Uzbek SSR); it began continuous operations in 1930.

The observations of all international latitude stations are coordinated at the Central Bureau of the International Polar Motion Service in the city of Mizusawa, Japan. The coordinates of the instantaneous pole of the earth are computed from the observations, and from them the polhode can be determined. Many astronomical observatories take part in studying the variability of latitudes and related phenomena, including the Soviet observatories in Pulkovo, Moscow, Poltava, Gorky, Kazan, Irkutsk, and Blagoveshchensk. In 1953 the Central Bureau of the Soviet Latitude Service was established at the Poltava Observatory. On the basis of observations made at Pulkovo, Poltava, Kitab, and Kazan, it computes the coordinates of the pole with sufficient accuracy for the practical needs of geodesy and the time service.