Comparison of Site Velocities Measured by VLBI and GPS in the Key Stone Project Network

Abstract

Communications Research Laboratory has established four space geodetic observation sites in and around Tokyo, Japan under the Key Stone Project (KSP) [KOYAMA et al, 1997]. At each of the four sites (i.e. Koganei, Kashima, Miura, and Tateyama), an 11-m antenna VLBI system, a 75-cm telescope SLR system, and a dual-frequency geodetic GPS receiver system are collocated closely with each other. The relative positions of the three reference points are repeatedly measured by ground survey measurements. The comparisons of the site coordinates and velocities estimated from three different space geodetic techniques are considered to be quite important to understand error sources of each measurement technique and to evaluate consistency of the coordinates and velocities defined in a conventional terrestrial reference frame. In this paper, site velocities estimated from VLBI and GPS observations are compared.