On the Use of Aeromagnetism for Geological Interpretation: 1. Comparison of Scalar and Vector Magnetometers for Aeromagnetic Surveys and an Equivalent Source Interpolator for Combining, Gridding and Transforming Fixed Altitude and Draping Data Sets
Résumé
Airborne magnetic surveys are common in geosciences. High precision surveys are usually performed at a low altitude, draping the topography, using scalar absolute magnetometers and active compensation systems to correct the disturbances generated by the carrier. Another solution is to measure the total magnetic intensity using vector magnetometers, which allows compensation for aircraft fields to be calculated directly, without compensation systems. This study uses data of an industrial airborne survey and of a vector magnetometer survey with a small overlapping area in the Vosges (France) to compare both datasets and shows that both solutions provide results of the same overall precision. This paper also addresses the issue of combining fixed altitude and draped level datasets as well as topographic effect management by proposing an equivalent source interpolator based on a set of simple dipole sources. A synthetic case shows that the equivalent source interpolator allows to compute grids of the magnetic anomaly as well as potential field transforms from a draped dataset with an error level a few orders of magnitude lower than could be obtained with minimum curvature, a classicaly applied interpolator. The interpolator is also tested on a case study in the Vosges massif of which geological interpretation is presented in Bertrand et al. (2020). The results confirm the observations made on the synthetic case and show that the equivalent source interpolator is more tolerant to navigation errors (altitude) than minimum curvature and allows more rigorous computation of potential field transforms of draped datasets.
Loading...