Compilation, back-calibration and standardization of aeroradiometric surveys from Namibia, Southern Africa

During 1992 and 1993 select portions of existing government airborne radiometric data covering almost 91,000 km2 of central Namibia were compiled into a master digital data set. This compilation involved the interactive, semi-automated digital recovery of approximately 42,000 line kilometres of original analogue chart traces. A further 49,000 line kilometres of digital data were also reprocessed. Available data represented ten different surveys collected over 12 years with a variety of spectrometers, spectral windows and survey parameters. Preliminary digital grids of each radioelement were compiled, verified and used to select representative sites for ground measurements within each survey block. Results obtained from the ground program were used to back-calibrate the airborne data, standardize the various surveys and convert airborne measurements into equivalent ground concentrations of uranium, thorium and potassium. The quality and consistency of final map products conclusively demonstrates that existing analogue radiometric data, in various states of preservation, can be successfully recovered, combined with modern digital data, and utilized to assist exploration, mapping and environmental studies. (author)