Systems for the determination of polar motion

The benefit of long-term observations of latitudinal variation is primarily the derivation of corrections to time and astronomical coordinates of control points. Other applications (those with which this report is concerned) include maintenance of an internationally accepted coordinate reference system, monitoring of the Earth's pole of rotation, and studies of the possible relationship of earthquakes to polar motion. Data produced by classical methods, since 1899, are insufficient to permit accurate prediction of polar motion, to determine the amount or existence of secular drift of the pole, or to detect the possible effects of earthquakes on polar motion. For these and other reasons, the international participants in the program agree that the program should be continued for at least another 50 to 100 years and that more accurate observation methods should be developed. The National Geodetic Survey, in its role as the United States' participant in the program, suggests a number of alternatives for solution of the problems enumerated and for consideration by the international community.