Geodetic astronomy in the united states

Abstract

The astronomical work of the U. S. Coast and Geodetic Survey is concerned mainly with the astronomy of position. Much of its work isbased on the labors of those who compile the standard star catalogues and determine the other fundamental constants on which the nautical almanacs and ephemerides of the world are based. Some of its work, however, such as the observations for the variation of latitude and for determining the figure of the earth may contribute to our knowledge of some of the fundamental constants of positional astronomy. Much of the astronomical work of the Survey consists of the determination of latitude, longitude and azimuth. To the astronomer there is only one kind of latitude, longitude and azimuth, the astronomical kind, and except for the motion of pole in the body of the earth, there is at any given place, only one value for each of these quantities. This value may be determined by observations made at the place in question and also, in the case of longitude, at some other place where the longitude is known. Apart from the necessity of a purely conventional prime meridian, the observations made at a point determine the quantities in question for that point quite without reference to their values elsewhere. To the geodesist, however, whose task it is to provide the basis for accurate maps and charts, astronomical observations alone are not sufficient basis for accuracy in his work. They may serve as