Gravity Meter Primary Station Net in East and Central Africa

Abstract

Summary Between 1958 and 1961 a net of accurate gravity meter stations was established in Tanganyika, N. Rhodesia and Nyasaland, with a few stations in Kenya, Uganda, S. Rhodesia and Bechuanaland. There are now 109 gravity stations in the area with a relative accuracy of better than 0.1 mgal, and an accuracy of about 0.5 mgal relative to the Potsdam system. The net was primarily intended to provide control for a regional gravity survey of Tanganyika, but has also served to connect several other formerly isolated gravity surveys to the international system. Most of the pendulum and gravity meter stations established by other observers before 1958 were reoccupied. When these sets of measurements are compared with the Overseas Geological Survey net individually there are slight differences of datum and calibration, but the mean discrepancies are negligible. The linearity of the calibration factors of the O.G.S. gravity meters was confirmed by a series of tilt-table calibrations. Before 1954 the Office de la Recherche Scientifique et Technique Outre-Mer had established several important chains of gravity meter stations from Europe, through North, West and East Africa to Madagascar. The O.R.S.T.O.M. values now appear to have been computed with an incorrect calibration factor but otherwise had a high relative accuracy.