AEROMAGNETIC GRADIOMETRY - THE STATE OF THE ART

There has been speculation in recent years regarding the advantages of airborne magnetic gradiometry for enhancing the detail in magnetic maps made by the conventional method of measuring the total field. However, it is only recently that the necessary instrumentation has been refined to the point that some of these advantages can be demonstrated. This paper outlines briefly the advantages of gradiometry and gives an overview of the instrumentation required. Particular emphasis is placed on the magnetic compensation subsystem because in gradiometry, where total field- measurements are differenced to a resolution of several parts in 10 7, the demands on magnetic interference compensation are very stringent. The NRC Convair-SSO's three-axis gradiometer system is used to illustrate gradiometer instrumentation. In recent surveys flown by the Convair 580, the lateral gradient was used to enhance detail in the direction perpendicular to the survey lines. Some results from this work are shown.