HR: 09:00h
AN: G51D-05 INVITED     [Abstracts]
TI: Testing monument stability with short-baseline GPS measurements
AU: * Williams, S D
EM: sdwil@pol.ac.uk
AF: Proudman Oceanographic Laboratory, Bidston Observatory Bidston Hill, Prenton, CH43 7RA United Kingdom
AU: Agnew, D
EM: dagnew@ucsd.edu
AF: Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AU: Wyatt, F
EM: fwyatt@ucsd.edu
AF: Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AU: Bock, Y
EM: ybock@ucsd.edu
AF: Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0225 United States
AB: The two permanent GPS sites at Pinon Flat Observatory (PFO)- called, naturally, PIN1 and PIN2 -are among the oldest permanent GPS sites in southern California. These sites were built in 1989 as prototypes for a continuous GPS network, an idea only just being implemented in a few places. The monumentation (how the GPS antenna was attached to the Earth) used at these sites was based on long experience operating several laser strainmeters at PFO, and is the basis for the drilled-braced monument design currently used by networks such as SCIGN and PBO. The record of GPS measurements between these sites provides long-term data between two closely spaced and well-anchored monuments, and so gives us a unique perspective on potential sources of noise such as monument stability, near field environmental effects and equipment effects. Because the two sites are only 50 meters apart, many sources of noise (and signal) are common to both, and cancels when we estimate the baseline vector between them. The day-to-day scatter in the baseline series (1-sigma 0.07 mm in the horizontal) is almost a factor of 10 smaller than is typical for a globally-referenced position series, and significantly less than the scatter from differencing the global series between these sites (0.35 mm). We present the results of a Maximum Likelihood Estimation (MLE) of the noise content which we assess in the context of monument stability. We also discuss an unexpected annual signal in the north-south component, a change in the white noise content attributable to an equipment change and outliers and offsets due to known local environment changes.
DE: 1206 Crustal movements--interplate (8155)
DE: 1208 Crustal movements--intraplate (8110)
DE: 1244 Standards and absolute measurements
DE: 1294 Instruments and techniques
DE: 1299 General or miscellaneous
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting