Gravity data were acquired using a LaCoste& Romberg model G (LCR G-65) relative spring gravimeter (Fig.
Calibration results of different type spring gravimeters from the repeated measurements of Estonian calibration lines.
On each point gravity acceleration was measured by relative spring gravimeter as well as height obtained by spirit levelling.
For evaluation purposes, we have carried out relative gravity measurement with the relative spring gravimeter LaCoste&Romberg model G on 8 stations of the network.
From 1970 to 1990 four gravity campaigns were carried out on the network by using a precise USSR manufactured spring gravimeter GAG-2.
Spring gravimeters and most likely an air transport were used for the connection measurements.
It was based on the determinations of absolute gravity values with a JILAg-5 gravimeter in 1995 as well as relative gravity connections with LCR (LaCoste&Romberg) G-type spring gravimeters.
Following this, advances included the (a-stable) relative spring gravimeters
, free-fall measurements made by dropping macroscopic objects and using the methods of geometrical optics to sense motion, and finally, free-fall measurements made using optical interferometry.
The survey was accomplished with four spring gravimeters
, three LaCoste & Romberg and a digital Scintrex gravimeter.
Thermostat is an essential precondition for the precise measurement with the relative spring gravimeters