This volume is based on an international symposium held in Rio de Janeiro. It gives a progress report on geodetic positioning with GPS. The maintenance and the densification of reference frames are treated for the purpose of establishing global and regional GPS networks. The scientific achievements of the South American Geocentric Reference System project (SIRGAS) are described. Several contributions review the state of the art of GPS analysis techniques, ambiguity resolution methods, as well as GPS antenna and site problems. Novel applications of kinematic GPS positioning and quality control issues of real-time GPS positioning are discussed.