For the MRS part the magnetometer is used to determine the Larmor frequency and for recording of fluctuations in the earth's magnetic field during the recording of a full MRS sounding, that can take 5-10 hours.
The magnetometer can also be mounted on the GCM pulling sled so CGM and magnetic data can be recorded simultaneously. In Denmark mag-surveys are primarily used for archaeological investigations.
The proton magnetometer is a Geometrics G-856 Magnetometer, which has a resolution of 0.1 nT and an accuracy of 0.5 nT. The cesium magnetometer is a Geometrics G-858 Magmapper, which has a much higher sensitivity than the proton magnetometers.