Upward continuation of aeromagnetic profiles

Abstract

Upward continuation is normally carried out by convolving grid operators with the data. Continuation height is restricted to units of data intervals and much information is lost around the boundaries. Continuation can be carried out in the frequency domain in which case no information is lost around the edges and continuation height is not restricted. In the case of aeromagnetic surveying where high density data are normally collected along flight lines 10 or 20 data units apart, it is desirable to use a one dimensional operator. This avoids interpolation problems, but assumes infinite strike. This paper describes the results of model and field tests designed to investigate the limitations of one dimensional upward continuation in the frequency domain. The field tests show that in practice, the technique is less restrictive than indicated by model tests. For routine surveys one dimensional continuation is acceptable. The model tests show that depth to bottom of source is important and a body may have an infinite response at one level but a finite one at another. This casts doubts on the need for drape flying.