Display and enhancement of gridded aeromagnetic data of the Solway Basin

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Abstract
The British Geological Survey has completed the conversion of both aeromagnetic and gravity survey records to a digital data base. This paper examines some of the uses of the aeromagnetic data base. Rendering digitized aeromagnetic data as a rectangular grid of interpolated anomaly values allows regional variations in subsurface magnetization to be displayed as images rather than contoured maps. Images of the magnetic field are more appropriate for visual interpretation and can be enhanced using standard methods of digital image processing. The optimum method is a combination of directional first-derivative filtering to impart the illusion of side illumination, with spectral colouring of the 8-bit range of DN, the former being used to modulate the brightness of the latter. As well as many of the known regional magnetic features of the Solway Basin, this method highlights several trends that were unsuspected.