Abstract

In a magnetic cartography process and apparatus, measurements are performed by magnetic field sensors placed in "fish" moved in the area to be mapped. Gradients are determined on the basis of the difference between the measurements supplied by two sensors at the same time, this applying to any pair of sensors, and/or on the basis of the difference between the measurements supplied by the same sensor at two different times, this applying to any sensor, which leads to at least one map of gradients which is broken down into a map of regional field gradients and a map of local field gradients. On the basis of the local field gradients, a determination takes place of the geological field relative to the area, or the gradients of the field and then the local field, by adding the geological field to the regional field determined on the basis of its gradients by an inversion and direct calculation method.

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