Abstract: Despite the
development of an impressive GPS
infrastructure for precise orbit determination
and many advances in GPS modeling and
analysis techniques, significant error sources remain.
As continuously operating GPS arrays
continue to be deployed throughout the world to
study geophysical processes with signals below 1 mm/yr, the
need to eliminate all systematic errors is critical. Multipath
represents one of the largest errors in GPS applications
today. There is currently no standard technique to
remove multipath errors in high precision GPS softwares used
by the geophysics community. Failure to correct for
the multipath environment at a GPS site produces a
time-varying systematic error in GPS estimates which
degrades the accuracy of the system.
We outline an approach for
correcting multipath errors that has been
developed by aerospace engineers for spacecraft attitude
determination. This technique uses the signal-to-noise
ratio (SNR) to estimate corrections to the GPS
phase observables. Although routinely collected by GPS
receivers, SNR data are not currently used in
high precision GPS softwares. This SNR based multipath
correction technique can be used both on
older datasets as well as new GPS data. And because the
technique uses SNR data collected simultaneously with the
phase data, it is sensitive to time varying changes at GPS sites.
Sites suggested by our colleagues
Herring SNR Directory
We are grateful to NSF for funding our initial work. A NSF graduate student fellowship
to Andria Bilich also funded this research.
