What is TeroGrav?

TeroGrav is a software package to process raw gravity observations from relative spring gravimeters. The end result is a list of mean gravity values for each observed point. It consists out of a preprocessing and an analysis module.

Preprocessing module

The spring in relative gravimeters elongates over time due creep in the material. This drift, which can reach 0.1-1 mGal per day, is removed from the measurements. Furthermore, the effect of the varying gravitational attraction of the Moon and Sun corrupts the data (effect is around 0.1 mGal) is also removed in the preprocessing step. For very accurate measurements, and only for stations near the coast, TeroGrav can remove the effect of the varying gravitational attraction of the ocean tides on the measurements (size of this effect is around 0.01 mGal).

Analysis module

Relative gravity observations only observe gravity differences. To convert them into absolute gravity values, they need to be tied to points where the absolute gravity value is known. Furthermore, in a normal gravity campaign some points are observed more than once. Therefore, our analysis module performs a network adjustment uses the least-squares method which estimates an accurate mean gravity value for each point.

Benefits

– It can read directly the raw output from SCINTREX gravimeters (CG3M and CG5).
– In addition to the dial value of LaCoste & Romberg gravimeters, it can use the voltage reading that indicates the position of the beam around the equilibrium position.
– It runs under Windows, Linux and MacOS.
– Usage of various gravimeters and absolute gravity points in one network adjustment analysis.
– Option to estimate the scale factor of the gravimeters if more than one absolute gravity point in the network is observed.