Geoid Undulation Computations at Laser Tracking Stations
Loading...
Date
1987-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University. Division of Geodetic Science
Abstract
Geoid undulation computations were carried out at 39 laser stations distributed around the world using a combination of terrestrial gravity data within a cap of radius 2° and a potential coefficient set (Rapp and Cruz, 1986b) up to degree 180. The traditional methods of Stokes' and Meissl's modification together with the new Molodenskii's method and the modified Sjoberg's method were applied. Performing numerical tests based on global error assumptions regarding the terrestrial data and the geopotential set we concluded that the modified Sjoberg's method is the most accurate and promising technique for geoid undulation computations. The numerical computations of the geoid undulations using all the four methods resulted in agreement with the "ellipsoidal minus orthometric" value of the undulations on the order of 60 cm or better for most of the laser stations in the eastern United States, Australia, Japan, Bermuda and Europe. A systematic discrepancy of about 2 meters for most of the western United States stations was detected and verified by using two relatively independent data sets. The cause of this discrepancy was not found. A correction due to the inconsistencies of the terrestrial data and the potential coefficients within the cap surrounding the laser station, called the "local average" correction improved the results by 30 cm and it seems necessary to apply this correction. For oceanic laser stations in the western Atlantic and Pacific oceans that no terrestrial data available, the adjusted GEOS-3 and SEASAT altimeter data were used for the computation of the geoid undulation in a collocation method.