Toward an optimal assessment of UAV vertical magnetic gradient arrangement

Abstract

Among the geophysical methods, magnetic surveys are ones of the most used and reliable techniques to investigate archaeological sites. These targets are usually shallow sources generating weak amplitude anomalies. The vertical gradient measurements are preferred to the magnetic fields since it has a better sensitivity to the magnetic contributions due to shallow sources (the gradient fields decay faster than the magnetic field) and a better ability to distinguish and separate interfering anomaly due nearby sources. Thanks to the large deployment of UAV (Unmanned Aircraft System) of the recent years, in this work, we arranged a gradiometric system, trying one of the first attempts of vertical gradient measurements by drones for archaeological applications. These mobile platforms help to cover very large areas (this should help to follow better the long and regular shape of buried buildings) maintaining the same resolution of traditional ground surveys, with less times and risk and over sites of difficult access. However, the measurement of vertical gradients in drone-borne magnetometry is generally not taken into consideration, as it poses additional challenges to the survey and successive data processing In this work, we arranged the magnetic sensors as a gradiometric system, obtaining a direct estimate of the vertical magnetic gradient in a single flight. We conducted our surveys with the Geometrics Micro-Fabricated Atomic Magnetometer (MFAM).