The radiometric, or gamma-ray spectrometric method, measures the natural variations in the gamma-rays detected near the Earth's surface as the result of the natural radioactive decay of potassium (K), uranium (U) and thorium (Th). The data collected are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. The terrestrial dose rate grid is derived as a linear combination of the filtered K, U and Th grids. A low pass filter is applied to this grid to generate the filtered terrestrial dose rate grid.
This GSNSW Exploration NSW Area M Kayrunnera dose rate grid geodetic has a cell size of 0.00048 degrees (approximately 50m) and shows the terrestrial dose rate of the NSW DMR, Area M, Kayrunnera(Milparinka, Cobham Lk, White Cl.), NSW, 1999. The data used to produce this grid was acquired in 1999 by the NSW Government, and consisted of 55448 line-kilometres of data at 250m line spacing and 60m terrain clearance.