From beaches to volcanoes: UAV applications in geoscience using high-resolution topography and aerial magnetic surveys.

Unoccupied Aerial Vehicles (UAVs) are transformative in the collection of geophysical, geodetic and geomorphology data. UAVs can rapidly collect data in areas that would either be difficult to access or time consuming to survey from the ground. Structure-from-Motion (SfM) is a powerful photogrammetry method for creating High-Resolution 3D topography from 2D imagery and is well suited to collection from a UAV. Repeated surveys of the same location allow morphological changes to be investigated. We demonstrate the potential of this method in monitoring changes in beach erosion in Pinellas County, FL, before and after a large storm event (Hurricane Michael, 2018), and after routine beach re-nourishment. Although SfM methods do not require a priori information on initial camera position, if the camera position is known accurately, highly accurate Directly Georeferenced models can be created quickly and with minimal need for Ground Control Points (GCPs). We demonstrate the capability of RTK (Real-Time Kinematic) enabled UAVs and assess the accuracy of the resulting DEMs both with and without GCPs. We find that PPK (Post-Processing Kinematic) solutions can result in models similar to those processed with GCPs, significantly speeding up the field survey procedure and minimising equipment costs. Aerial Magnetic data has long been used by exploration industry but due to cost has often been beyond the reach of individual academic researchers. Recent advances in sensors and in heavy-lift UAVs have allowed this powerful geophysical survey method to be used in natural hazards geoscience research. We present data from UAV magnetic surveys of volcanic features in Idaho and compare our results to those collected over years of ground magnetic data acquisition, demonstrating the potential of this method in geophysics research.