Total-field magnetometers (PPM) measure the scalar magnitude of the resultant field projected onto the ambient field direction, while fluxgate magnetometers (FGM) measure a specific vector component (e.g., vertical); for a fixed body/geometry the two anomaly types are linearly related.
The total-field anomaly measured by a PPM is essentially the component of the anomalous field vector projected onto the direction of the Earth's ambient field,...
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