The impact of VLBI and GPS on geodesy

Two new technologies, Very Long Baseline Interferometry (VLBI) and the Global Positioning System (GPS), will provide the means for achieving the perennial goal of geodesists—a unified, worldwide geodetic control point network tied to an inertial reference system. VLBI will replace optical methods for determining both polar motion and rotation rate, with accuracies an order of magnitude better and with results available a week or less after observations. GPS will permit rapid, economical point positioning with accuracies of a few centimeters over distances of 100 km or more. The potential of these new systems will generate new applications for geodesy and require a reevaluation of the role of geodesists