Use of absolute values of acceleration of gravity to obtain the scale factor of Lacoste&Romberg Model G gravimeters

Abstract

The Military Geographic Institute (IGM) is the institution responsible for maintaining and updating the official geodesic reference system of Chile put into effect through the National Geodesic Network (RGN), which consists of the Horizontal and Vertical RGNs. This latter element is made up of the leveling network, constituted by altitude points referenced to the Mean Sea Level (M.S.L.) and the Gravimetric Network, consisting of absolute and relative stations, with gravity acceleration values (g), referenced to the International Gravity Standardization Network 1971 (IGSN-71). The IGSN-71 was adopted as the world reference for gravimetric measurement at the 25th General Assembly of the International Union of Geodesy and Geophysics (IUGG) in 1971 with a precisión of ± 0,1 mGal. This current research work is mainly focused on making known the chief features of the operation and correct use of the instrument measuring the gravity acceleration (g) that the IGM uses for its gravimetric projects. The instrumental calibration procedure is made known here, obtaining the “scale” (adjustment) factor for each Lacoste&Romberg model G gravimeter in order
to obtain more accurate gravity values.The above is sustained in relation to the requirements suggested by international organisations in the area of geodesy, such as the International Association of Geodesy (IAG) and SIRGAS, which encourage all nations to implement homogeneous and precise global vertical reference systems, in which gravimetry is an essential factor in setting up a new vertical reference frame for the whole country, adopting physical heights.