A Quantitative Comparison of Low-Cost Structure from Motion (SfM) Data Collection Platforms on Beaches and Dunes

Observations of beach and dune geomorphology are critical for characterizing coastal processes and hazards. A relatively new approach for monitoring the coastline is Structure from Motion photogrammetry (SfM), a technique that uses overlapping photographs to reconstruct three-dimensional surfaces. In this study, a quantitative comparison of multiple low-cost kite-, pole-, and unmanned aerial vehicle (UAV)-based SfM data collection platforms is performed to illuminate important considerations when choosing an SfM platform for use in measuring beach and dune topography. A multicriteria analysis based on SfM results and platform usability is used to complete this comparison. Results show that UAV-based platforms received high performance scores, largely because these stable, high-flying platforms provide images with adequate texture to allow accurate three-dimensional topographic reconstruction. Although data extracted from the kite- and pole-based systems are less accurate, these platforms possess increased usability because of decreased barriers to entry and fewer environmental limitations (in the case of the pole), which increases their overall performance. These results illustrate that the overall effectiveness of a platform is based on many factors beyond vertical error of extracted data, and factors of platform usability can be important to consider when choosing an SfM platform. Furthermore, this multiplatform analysis reveals the important idea that different platforms can be optimal for different applications depending on the study site and environmental conditions. As the technology progresses, many improvements to platforms are likely to emerge, allowing SfM to become an even more useful tool for the coastal scientist.