Astronomical Point

(also astropoint), a point on the earth’s surface whose latitude, longitude, and azimuth of direction relative to some terrestrial object are determined by astronomical observations. At certain astronomical points, one or another of these quantities may be left undetermined. If the astronomical point coincides with the trian-gulation point and all three astronomical quantities are defined for it, it is called a Laplace point. In the triangulation of classes I and II in the USSR, astronomical points are determined at 70–100 km intervals. Besides ordinary astronomical points, there are basic reference points at which the astronomical longitude is determined with particular accuracy and thoroughness. They are used to determine the personal errors of an observer.