Although most modern relative-gravity meters provide real-time tide correction based on station location, GSadjust provides the option to replace the meter-provided tide correction with calculated tides using the Agnew model, from the software Predict, or from a Tsoft-format text file. The tide correction is changed using the Process > Tide correction menu item. This shows a dialog box in which the method can be selected:
Note: The Agnew code was originally developed for PyGrav (Hector and Hinderer, 2016). The accuracy of this code has not been independently verified.
Meter-supplied
If the tide model has been changed after loading a data file (using one of the options below), selecting Meter-supplied in the dialog will restore the original meter tide correction. If the tide model has not been changed, this option will have no effect.
Agnew
The Agnew correction calculates a theoretical solid-Earth tide based on station and time (Agnew 2007, Agnew 2012). The station occupation times must be recorded in UTC. The tide is calculated for a single location. When the Agnew option is selected, the user is prompted to enter coordinates:
The default coordinates are calculated as the average of the station locations.
Agnew, D.C., 2007, 3.06 - Earth Tides, in Schubert, G. ed., Treatise on Geophysics, Amsterdam, Elsevier, p. 163–195.
Agnew, D.C., 2012, SPOTL: Some Programs for Ocean-Tide Loading
Hector, B., & Hinderer, J. (2016). pyGrav, a Python-based program for handling and processing relative gravity data. Computers & Geosciences, 91, 90–97. https://doi.org/10.1016/j.cageo.2016.03.010
Van Camp, M., & Vauterin, P. (2005). Tsoft: graphical and interactive software for the analysis of time series and Earth tides. Computers & Geosciences, 31(5), 631–640. https://doi.org/10.1016/j.cageo.2004.11.015
