Ashton thorium grid

The radiometric, or gamma-ray spectrometric method, measures the natural variations in the gamma-rays detected near the Earth's surface as the result of the natural radioactive decay of potassium, uranium and thorium. The data are collected on airborne geophysical surveys conducted by Commonwealth, State & NT Governments and the private sector.

放射性测量法（radiometric），又称伽马能谱法（gamma-ray spectrometric method），可测量地球表面附近探测到的伽马射线的自然变化，此类伽马射线源自钾、铀、钍的天然放射性衰变。此类数据采集自由英联邦、各州及北领地政府以及私营部门开展的航空地球物理调查。