Comparison of Flight Height Controlled UAV and Ground Vector Magnetometer Survey Data Covering an Urban Landfill

Abstract

An autonomous UAV-mounted 3-axis fluxgate vector magnetometer (FVM) was flown over a Golden, Colorado landfill to test map buried ferromagnetic objects and infrastructure. The flights test terrain following flight control software using active GNSS positioning over a fixed 1-meter (m) resolution LiDAR control surface, at slung sensor clearances that approach ground survey sensor heights. The FVM was first walked over the landfill with the sensor at a constant 2 m above the surface, to provide a high-resolution ground survey dataset for comparison. Both the UAV and ground FVM data are scalar calibrated on the ground through a full sphere to return error corrected and 360⁰ maneuver compensated total magnetic intensity (TMI). The comparison also includes UAV downward and ground survey upward continuation filtered (DCF and UCF) TMI respectively, to put the two surveys on approximately the same levels, providing two inverse-distance-magnetic-source viewpoints for both surveys, one at ground level and one at UAV level. The UAV survey DCF results indicate that low level flights might be considered as a replacement for coarser reconnaissance ground TMI surveys in some mapping situations. Lastly, the ground and UAV survey calibration data statistics are reviewed, and the FVM survey TMI images are compared with each other. These in turn, are compared with a highresolution alkali-vapor scalar magnetometer (AVM) benchmark TMI survey, walked on the same lines as the FVM. The AVM provides a reference standard to compare with both FVM surveys.