All rocks and soils are naturally radioactive, containing various proportions of a variety of radioactive elements. Gamma-ray spectrometry provides a method of measuring concentrations of individual radioelements (in particular, K, U, Th) as the basis for mapping rocks by virtue of their characteristic radioelement signatures.

The GSC's National Gamma-Ray Spectrometry Program (NATGAM) has a long, productive and varied history, and offers a wide variety of geophysical products and services.

For over 25 years, GSC has conducted airborne (fixed-wing and helicopter) and ground gamma-ray spectrometry surveys over diverse geological terranes. The aerial surveys have been carried out in-house by the GSC's Skyvan aircraft (1968-1995) as well as by contractors, with subsequent ground followup by geologists.

In the past few years, there has been an increased emphasis on environmental programs as well as joint mineral resource development projects with industry and the provincial geological surveys.