Experimental Observation of boudary layer and movement of topographically varying desert dunes with unmanned systems

Desert dunes offer unique geophysical interactions, and these aeolian dominant interactions occur over a significant portion of earth surfaces. We pursued whether the movement of desert dunes can be accurately measured using unmanned aerial systems (UAS) data and a structure-from-motion as well as tracking boundary layer propagation and change in the topography during the boundary layer interaction. This volatile landscape makes an ideal setup for tracking imagery combined with the effect of atmospheric data.

For the photogrammetry data, datasets collected starting in 2018 of the Little Sahara dunes in northwest Oklahoma using a RGB camera attached to an UAS and flown along a set path. A 3D model of the dunes was created using Agisoft Metashape for each year’s data set to output a digital elevation model (DEM) using these images. After acquiring the DEMs, they were analyzed and coordinated in ArcMap. Finally, using ENVI and the add-on CosiCorr, the movement of the dunes could be estimated and shown with a vector field. Viewing transects of the of the same section of the dunes shows noticeable and evident changes over time. More recent datasets included focusing on the dune where the atmospheric data was collected with the intent of using the GIS exports to recreate the structure of the dunes to provide usable 3D models of the surface of the dune.

Atmospheric profiles were flown using UAS with an ultrasonic anemometer onboard. Since the wind comes predominately from the South at the site, the profiles progressed from an upstream location to a downstream location. Initial flights were manually flown remotely from approximately half a mile away, and multiple aircraft were utilized to keep an eye on the flight progress and how close the UAS was to the ground during each flight. Recent data was collected using Mission Planner to automatically fly the vertical profiles while tracking elevation changes and time stamps that can be matched with ground station anemometers to compare data as it changes due to the dune’s presence. The data is promising, despite some noticeable noise, and shows the wind acting as expected – flowing smoothly over the crest before becoming turbulent at the base of the leeward side.