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Subdaily signals in GPS observations and their effect at semiannual and annual periods
Author(s) -
King Matt A.,
Watson Christopher S.,
Penigel T.,
Clarke Peter J.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl032252
Subject(s) - amplitude , global positioning system , geodesy , nyquist frequency , geology , environmental science , sidereal time , geophysics , remote sensing , physics , computer science , telecommunications , computer network , bandwidth (computing) , quantum mechanics , astrophysics
Estimates of seasonal geophysical loading from GPS may be biased by propagated unmodeled subdaily signals. Although the major geophysical signals at semidiurnal and diurnal frequencies are now routinely modeled in GPS analyses, the characteristics of unmodeled or mismodeled subdaily signals are not well known. Here, using site coordinates estimated every 5 minutes, we examine the subdaily coordinate spectral characteristics for ∼90 global GPS sites. Unmodeled signals with amplitudes at the 10 mm level are present at frequencies between ∼1/day and the Nyquist frequency. These are shown to propagate into 24 h solutions with (among other frequencies) annual and semiannual periods with amplitudes up to 5 mm, with a median amplitude in the height component of 0.8 mm (annual) and 0.6 mm (semiannual). They are shown to bias low‐degree spherical harmonics estimates of geophysical loading at the level of 5–10%, although the exact effect will be network dependent.