IN-SITU UTILITY OF UNMANNED AERIAL VEHICLES (DRONES) FOR GEOLOGIC FIELDWORK

The use of unmanned aerial vehicles (UAVs) for geologic fieldwork is increasingly popular. UAVs allow geoscientists to connect two traditional scales – local (boots-on-the-ground) and regional (satellite) – thereby providing a greater range of views across three dimensions and increasing accessibility to data in the form of high-quality imagery. At present, the geology literature with UAVs focuses almost exclusively on post-processed imagery (e.g., structure from motion photogrammetry, spectral sensing data). However, UAVs also have in-situ utility to geoscientists (e.g., reconnaissance, following a feature), and given the relatively low cost of commercial UAVs, the benefits of in-situ imagery are accessible to many geoscientists. Here, we present observations from three case studies about how geoscience experts use UAVs to improve their interpretations of transpression-induced deformation in the Mecca Hills in Southern California.

Three experts were asked to complete three field scenarios (one day per scenario). 1. Interpret a large-scale vertical outcrop from the ground, then fly the UAV and see if the availability of in-situ imagery (from down-plunge view) changes the interpretation or confidence in the interpretation. 2. Conduct an initial field area survey to consider regions of interest, then fly the UAV for further exploration. 3. In a structurally complex area that has four existing (and competing) models of fault interaction, fly the UAV to evaluate the models in-situ and tease apart what is happening. We observed experts flight strategies could be characterized using a two-by-two matrix of scale (narrow, wide) and method (data-driven, model-driven); e.g., experts who initially had no strong model for what was happening on a wide scale would fly to get a broad-view and look for interesting features, but once experts developed a wide scale model they would run a t-flight, flying along strike and then perpendicular to strike. We also observed that the new perspectives and orientations provided by the UAV in-situ presented new challenges for the visual interpretation of geologic processes; e.g., experts often reported not knowing where they were in space, not understanding where the UAV was “looking”, and feeling overwhelmed with what the UAV sees.