Modeling Stratigraphic Architecture Using Small Unmanned Aerial Vehicles and Photogrammetry: Examples From the Miocene East Coast Basin, New Zealand

Abstract

Abstract: The ability to view and characterize outcrops that are difficult to study from the ground is greatly improved by aerial investigation. We describe the application of flying a small, unmanned aerial vehicle (UAV) to collect photographic data for modeling rock outcrops and creating detailed digital terrain models (DTMs), which can be used for multi-scale digital feature mapping in true three-dimensional (3-D) space. Georeferenced digital outcrops can complement field measurements, as well as enhance classroom to field learning experiences for undergraduate education. High-resolution photographs, acquired at various elevations and azimuths by a small UAV, are used to convert stratigraphic features to 3-D digital representations with spatial accuracy approaching 1 cm. Complex topography, recorded in 2-D image sequences, is rendered digitally in 3-D surface models using Structure from Motion (SfM) photogrammetry. The resulting DTMs are populated with the high-resolution photographs for stratigraphic interpretation at the centimeter scale. The method of imaging and modeling outcrops is demonstrated in the Miocene East Coast Basin, New Zealand, where steep, coastal cliff exposures of continental-slope deposits and extensive, wave-cut platform exposures of steeply dipping, deep-water basin deposits offer exceptional opportunities to investigate depositional processes and the resulting stratigraphic architecture. Our approach makes it possible to characterize deposits that are exposed in inaccessible, 150-m-high, vertical sea cliffs and along 2000 m of wave-cut platforms, and to quantify their geometric variability. Results yield a spatial and temporal understanding of two depositional systems at a scale that was previously unattainable by conventional field techniques.