Summary
NGU owns and uses a set of transportable concrete calibration pads for calibration of its airborne
gamma-ray spectrometers. The pads are principally designed for hand-held instruments, in contrast with
larger fixed pads which are specially designed for airborne systems. Such a set of fixed pads are
maintained by the Swedish Geological Survey (SGU) at Dala airport, Borlänge. In August 2012 NGU's
airborne system was calibrated using the Borlänge pads, allowing a comparison between transportable
and fixed calibration pads. A comparison of the two calibration methods shows little significant
differences. As such NGU's calibration pads are a suitable and convenient substitute for dedicated fixed
calibration pads. Calibration parameters obtained in recent years from the NGU pads are also provided
as a monitor of long-term instrument stability.
