The natural gamma radiation emitted by potassium, uranium and thorium is attenuated by snow. This attenuation depends on the water-equivalent of the snow layer. Air absorption coefficients were determined by flying at different altitudes over a uniform test strip and used to calculate the absorption coefficients for water. Results using the Geological Survey of Canada high sensitivity airborne gamma-ray spectrometer showed that snow water-equivalents up to 18 cm could be measured to an accuracy of 2 cm over suitable terrain. The importance of temperature and soil moisture corrections are discussed, together with statistical, instrumental and navigational errors.

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