Scalar, vector, tensor magnetic anomalies: Measurement or computation?

Magnetic measurements most often correspond to the measurement of the magnitude of the earth’s magnetic field while the magnetic field is a vector. Assuming that the magnetic anomaly has low amplitude, the theory shows that it is possible to calculate the vector field. But this assumes to know the earth’s magnetic field direction and, for some applications, that of the magnetization. These assumptions can be severe limitations to interpretations. It is very likely that inertial measurement units will be available soon and combined to three-component fluxgate magnetometers, measurement of the earth’s magnetic vector will be possible with sufficient accuracy. Superconducting quantum interference devices also need to be combined with inertial measurement units. They allow the measurement of the nine gradient components of the total magnetic field with an excellent accuracy. But difficulties of implementation must be overcome so that their use becomes general.