Facilitates geologic interpretation of an aeromagnetic survey of the Oregon Cascade Range by calculating the magnetic field caused by a 3-D topographic model. Maps of the calculated field are compared with observed aeromagnetic data both visually and with a numerical technique that produces a contour map of correlation coefficients for the model. These comparisons allow quick recognition of anomalies caused by normally or reversely magnetized topographic features and, more importantly, identification of anomalies caused by geologic features not obviously caused by the topography. -from Authors