New horizons for airborne geophysical mapping

Abstract

Survey technology is entering a new age of maturity which seems destined to make airborne geophysics an even more important solution to many exploration problems. In terms of quantity, more than 40 years of aeromagnetic survey gives an emerging completeness of reconnaissance coverage world-wide. In terms of quality, superlative resolution of geological detail is evident in surveys (magnetic and radiometric) carried out to the latest specifications. The steady accumulation of aeromagnetic survey data is approaching first-pass completeness, even in areas of the world where this has not been deliberately planned. While the technical quality of older surveys often leaves something to be desired, even the poorest early data can give valuable new structural information when digitized and compiled together into maps covering large areas at small scales. Such a compilation of North America was published in 1987. Compilations of Europe, Africa and Australia will be completed in time to display at this meeting. Some new technological solutions for digitizing map data, linking and levelling separate surveys and the incorporation of long wavelength (near-DC) information will be described. The quest for high resolution in magnetic and radiometric surveys is surprisingly new and distinctly Australian. The need for low ground clearance and close line spacing is predicted by simple theory, and new technology can cope with the consequent demands of accurate position fixing, more frequent sampling of geophysical parameters with low noise envelopes, high-resolution magnetic recording and adequate crystal volumes for spectrometry. Current techniques of imaging the resulting data ? both magnetic and spectrometric ? test the data quality to its limits, and suggest new areas where improved data acquisition and processing technology could stretch the exploration power of airborne surveys even further in the immediate future. Meanwhile, the full digital integration of geophysical information with geological and other geo-data is still in its infancy.