Precision Surveying Using Radio Interferometry

The application of Very long baseline Interferometry (VLBI) to surveying is reviewed. An examination of the error budget for the VLBI observing system in use by the GSFC/HO/MIT VLBI team is presented, and methods for decreasing the effects of the various errors sources are reviewed. Results from recent VLBI experiments are presented. These results show millimeter level repeatability on a baseline 1.4-km in length and 10-cm level repeatability on a 4,000-km baseline from Massachusetts to California. Results for polar motion and UT1 determined from VLBI observations are presented and compared with determinations from the Bureau International de l'Heure, the primary international service for polar motion, and with the determinations from the Doppler Satellite System. The Doppler and VLBI determinations are seen to exhibit a common trend not seen in the BIH values.