Canada - Grid Spacing: 250m - Airborne Radiometric - Equivalent Thorium, eTh

The airborne gamma-ray spectrometry (AGRS) data in the GDR were acquired by a series of more than 370 surveys over 30 years, from about 1970 to 2013, using a variety of aircraft and instrument packages. The aircraft flew along a pattern of parallel flight lines typically at 120 m terrain clearance (height above the ground). The flight line spacing includes 200-500 m, 1000 m, 5000 m and some at 25000 m. Typically, aircraft fly at a speed of 120 knots (190 km/h). Most data were acquired by sampling (counting) at 1 second intervals (some of the oldest data were sampled every 2.5 seconds), which is equivalent to about 60 m on the ground. Data acquired are processed to generate the natural air absorbed dose rate, concentrations at ground level of potassium, thorium, and uranium, as well as ratios of these elements to one another.