Realization of the ITRF-94 in Thailand and Malaysia by Use of a Combined Network for Geodynamics and National Survey

In 1994 and 1996, two major GPS campaigns for geodynamics, named GEODYSSEA, were conducted in South East Asia. The paper gives an introduction to the GEODYSSEA project and its results. In cooperation with the national survey authorities, this occasion was used to realize the ITRF in several countries of South East Asia. This paper describes the background and results of GEODYSSEA and the additional measurements as well as transformations of the national datums of Thailand and Malaysia to the ITRF-94. By use of the GEODYSSEA data and also by repeated occupations of the first order stations in the respective countries an accuracy of 2 cm in position and about 3 cm in height was obtained for the ITRF-94 coordinates. Depending on the accuracy of the existing local coordinates the transformation parameters between the national datum and ITRF-94 were determined with and accuracy of 5 to 10 cm.