Gamma-ray mapping is a geophysical technique that measures the natural radioactivity emitted by elements in the soil and near-surface rock — primarily potassium (K), uranium (U), and thorium (Th). These elements occur naturally in different concentrations depending on soil type, texture, and mineralogy.
A gamma-ray sensor detects the energy and intensity of this radiation as it moves across the landscape. Because different soil types and mineral compositions emit characteristic gamma-ray spectra, the resulting data can be used to map soil properties, detect anomalies, and identify geological features with high spatial resolution.
Medusa sensors measure the full gamma-ray energy spectrum, which allows for simultaneous quantification of K, U, and Th concentrations, as well as total dose rate. The onboard mDOS software processes and logs these measurements in real time, making it possible to produce detailed maps directly in the field.