REMARKS ON HOUGUER ANOMALY

Abstract

The different approach to gravity observations as between geodesists studying fundamental problems of the earth and geologists interested in local relationships is discussed. Attention is drawn to the significance of the variation between the geoid and spheroid in the case of gravity surveys, and discussed in terms of the results of a National Mapping Geodetic Survey in the Woomera area. The need for an Australia-wide map of the variation between geoid and spheroid is highlighted.

In relation to localised gravity surveys, as in the case of oil exploration, the limitations inherent in standard Bouguer Anomaly Maps developed from semi-detailed surveys (traverses several mites apart) are analysed. The advantages gained by observing such surveys by the horizontal gradient method are outlined. Experience gained in use of this method in micro-gravity surveys is discussed.

The value of the horizontal gradient method for use in obtaining observed derivatives and calculation of depth estimates is referred to. Exploitation of the horizontal gradient technique in oil exploration is recommended.