Aeromagnetic data are routinely presented as contour or color-shaded maps of the total magnetic intensity (TMI). An interpreter's task is to identify features (anomalies) contained within the map and qualitatively and/or quantitatively interpret them into geologic structures at depth. If the map contains anomalies that have large magnetic intensities, the bodies might be considered to have large magnetizations, or to be at shallow depths. Small amplitude anomalies superimposed on these anomalies could be masked or even missed by an interpreter. Thus the task of the interpreter is to use the spectral content of the anomalies to try and resolve these ambiguities. Part of this process is also to obtain estimates of the depth and shape of the body causing the anomalies.