At the poles, the field is concentrated and therefore has a high intensity. A magnetometer would read 61,000 nT area at the poles. In a localised rea, the magnetic field tends to be quite even. The amount of disturbance is a function of the mass of the object. 3.4.1 Introduction Magnetometers are typically towed devices, comprising a towfish, a cable and a topside data-logger.
Modern systems display the digital readout in graphic format on a PC or some graphic interface.
Magnetometers vary widely in size and shape. Some common examples are shown below. Thus caesium magnetometers, although more expensive to purchase or hire, can be towed at higher speeds and allow greater survey coverage. The proton precession magnetometer is easiest to understand, so we will concentrate on this in the lecture. The proton precession magnetometer is the most popluar magnetometer used in marine magnetic surveys.