Abstract
The general problem of analysing the depth of near surface magnetic sources which contribute to the magnetic anomaly spectrum has been analysed in terms of crossings per unit interval. Assuming a random distribution of either magnetic poles or magnetic dipoles aligned in any of three orthogonal directions, explicit functions have been derived expressing the crossings per unit interval for three orthogonal field components directly in terms of either the depth to a thin layer or depth to the top of a thick layer.
The statistical weakness of the method is explained: it appears to be most useful in supplementing other statistical techniques. The speed and simplicity of the method, however, makes it an attractive possibility in extracting preliminary information from the large number of World Magnetic Survey aeromagnetic three-component profiles now being acquired.
