An optical processor has been used to filter aeromagnetic contour maps in order to obtain information on underground magnetic ore deposits. This was accomplished by directional filtering of the spatial Fourier transform of the contour map. The directional filtering yields maps of gradients having given directions. A digital analysis was also performed on the data so that the feasibility of the optical technique could be evaluated. The results obtained so far suggest that a systematic filtering of aeromagnetic maps can be carried out at low cost and that the filtered maps can yield useful information to the interpreter.
H. H. Arsenault, M. K. Séguin, and N. Brousseau, "Optical Filtering of Aeromagnetic Maps," Appl. Opt. 13, 1013-1017 (1974)