DOWNWARD CONTINUATION USING THE MEASURED VERTICAL GRADIENT

Abstract

The availability of two independent measured quantities, the total magnetic field and the vertical gradient of the total field, allows a solution to the downward continuation problem not heretofore practical. The method proposed in this short note uses the Laplace equation and a Taylor series expansion but does not require the numerical solution of an integral equation derived from potential theory. Evjen (1937) discussed the use of this technique for the gravitational field; however, he did not advocate the method because of the practical difficulties involved in making the gradient measurement. It is the purpose of my note to point out the utility of this direct method and to discuss the details of its application to airborne gradiometer survey data now being collected.