Airborne geophysical surveying is a process of measuring the variation in several key physical or geochemical parameters of the earth. The most important parameters measured are conductivity (which is the inverse of resistivity), magnetic susceptibility, density, and radioactive element concentration. Any change in the earth's near surface that causes a measurable change in these parameters presents a potential application for airborne geophysics.
Electromagnetic surveys map the three dimensional variation in conductivity, caused by changes in mineralogy, intensity of alteration, water content or salinity. Airborne magnetic surveys map the variation of the magnetic susceptibility, generally due to changes in the magnetite content of the rock. Gamma-ray spectrometric surveys measure the radiation of one or more of the natural radioelements: potassium, uranium, or thorium, or a specific man-made radioelement. Airborne gravity surveys map density variations within the earth.