Gamma-ray mapping provides information about the elemental composition of the topsoil, which correlates with a range of physical and chemical properties. Key soil properties that can be mapped include:
- Soil texture – Clay content and sand/silt ratios are strongly correlated with potassium (K) and thorium (Th) concentrations.
- Organic matter – Indirectly inferred from spectral patterns in combination with other measurements.
- Soil type and parent material – Different geological formations produce characteristic gamma-ray signatures.
- Soil moisture – The gSMS-100 uses the attenuation of gamma radiation to directly measure volumetric water content.
- Soil density – Gamma-ray attenuation can be used to infer bulk density in certain configurations.
- Radioactive contamination – Anomalies in U, Th, or artificial radionuclides (e.g. Cs-137) can indicate contamination.
The exact correlations vary by region and geology, so surveys are often calibrated with soil sample data from the study area to improve accuracy.