TeroGrav is a software package for processing raw gravity observations from relative spring gravimeters. The result is a list of mean gravity values for each observed point. It consists of a pre-processing module and an analysis module.
The spring in relative gravimeters elongates over time due to creep in the material. This drift, which can reach 0.1-1 mGal per day, is eliminated from the measurements. Furthermore, the data is pre-processed to remove the corrupting effect of the varying gravitational attraction of the Moon and Sun (around 0.1 mGal). For highly precise measurements, particularly for coastal stations, TeroGrav can also account for the effect of the varying gravitational attraction of ocean tides on the measurements (with an effect size of around 0.01 mGal).
Relative gravity observations only observe gravity differences. To convert them into absolute gravity values, they must be referenced to points with known absolute gravity values. Furthermore, in a normal gravity campaign, certain points are observed multiple times. Therefore, our analysis module employs a network adjustment using the least-squares method, which calculates precise mean gravity values for each point.