CONTEMPORARY SPACE GEODESY AND REFERENCE FRAMES

Abstract

Global coverage of landmass by a network of reference GPS stations has principally changed the interpretation of the observation of active processes on the Earth using modern space geodesy. The problem of realization of the unified reference frame became one of the main factors for the correct processing of GPS measurements and their interpretation. The commonly accepted International Terrestrial Reference Frame (ITRF2000) is based on joint adjustment of various observations, including GPS data, Very Long Baseline Radio Interferometry (VLBI), and Satellite Laser Ranging (SLR) with corner reflectors. The analysis of specific features of the determination of the ITRF2000 and other similar geocentric system indicates that the residual velocity of the reference frame origin can distort the interpretation of the deformation field observed at the Earth's surface using the global GPS network. In order to avoid this distortion, it is necessary to introduce a correction of the reference origin displacement into the estimated parameters along with the calculation of the Euler vectors describing momentary relative motion of stable fragments at the Earth's surface. The approach described here was tested to correct various a priori reference systems, including ITRF2000, NUVEL_1A, and the so-called motionless frame. These tests yielded similar estimates of large-scale motions of the Earth's surface. The results demonstrate the stability of the suggested method and high resolution of the modern global geodynamic network, including its segment in northern Eurasia.