We examine the electromagnetic coupling of a GPS antenna–monument pair in terms of its simulated affect on long GPS coordinate time series. We focus on the Earth and Polar Observing System (POLENET) monument design widely deployed in Antarctica and Greenland in projects interested particularly in vertical velocities. We base our tests on an absolute robot calibration that included the top ∼0.15 m of the monument and use simulations to assess its effect on site coordinate time series at eight representative POLENET sites in Antarctica over the period 2000.0– 2011.0. We show that the neglect of this calibration would introduce mean coordinate bias, and most importantly for velocity estimation, coordinate noise which is highly sensitive to observation geometry and hence site location and observation period. Considering only sub-periods longer than 2.5 years, we show vertical site velocities may be biased by up to ±0.4 mm/year, and biases up to 0.2 mm/year may persist for observation spans of 8 years. Changing between uniform and elevation-dependent observation weighting alters the time series but does not remove the velocity biases, nor does ambiguity fixing. The effect on the horizontal coordinates is negligible. The ambiguities fixed series spectra shownoise between flicker and randomwalk with near-white noise at the highest frequencies, with mean spectral indices (frequencies <20 cycles per year) of approximately −1.3 (uniform weighting) and −1.4 (elevation-dependent weighting). While the results are likely highly monument specific, they highlight the importance of accounting for monument effects when analysing vertical coordinate time series and velocities for the highest precision and accuracy geophysical studies.

Item Type:	Refereed Article
Keywords:	GPS, time series, monumentation effect, phase centre variation, velocity accuracy
Research Division:	Engineering
Research Group:	Geomatic Engineering
Research Field:	Geodesy
Objective Division:	Environment
Objective Group:	Climate and Climate Change
Objective Field:	Climate and Climate Change not elsewhere classified
Author:	King, MA (Professor Matt King)
ID Code:	89659
Year Published:	2012
Web of Science® Times Cited:	7
Deposited By:	Geography and Environmental Studies
Deposited On:	2014-03-11
Last Modified:	2014-06-12
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