HR: 10:50h
AN: G52A-03 INVITED    [Abstracts]
TI: Vertical Ground Motion Measurements with GPS
AU: * Herring, T A
EM: tah@mit.edu
AF: EAPS/MIT, 54-820A, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
AB: In this talk we discuss the measurement of vertical ground motion with the Global Positioning System (GPS). The measurement of heights with space based geodetic systems are intrinsically less accurate than measurements of horizontal positions because of the distribution of signals from only the upper hemisphere of the sky and because of the correlation between atmospheric propagation delays and the estimates of height. In addition, for GPS, the effects of phase changes through and around the antennas and radomes are strongly elevation angle dependent and effect the determinations of heights. Over relatively short distances, less than a few hundred kilometers, the atmospheric delays and geometry limit the precision of relative height measurements, averaged over 24-hours, to 2-3 mm. Over longer distances and for height measurements in a global reference frame effects for phase patterns on the GPS satellites and the effects of orbital modeling effect the accuracy of height measurements. These latter effects limit the height precision to 5-10 mm. Temporal averaging reduces the noise in height measurements but systematic effects from satellite antenna patterns and possibly long term orbital effects limit the accuracy of height rate measurements. We show GPS results from a variety of spatial and temporal scales and assess the accuracy characteristics of GPS determination of height.
DE: 1200 GEODESY AND GRAVITY
DE: 1209 Tectonic deformation (6924)
DE: 1241 Satellite geodesy: technical issues (6994, 7969)
DE: 1243 Space geodetic surveys
DE: 1295 Integrations of techniques
SC: Geodesy [G]
MN: 2007 Fall Meeting