Hydro-informatics and Innovative Technology
Generating a Digital Elevation Model from the Structure-from-motion Technique in a Peruvian Ephemeral River
Wednesday, January 4
12:30 PM - 12:30 PM
Location: 5th Meeting Room
Peru exhibits serious limitations in river geomorphological. Remote sensing technologies such as LiDAR and structure-from-motion (SfM) have proved to have the potential to provide actionable geomorphological data. SfM couples the capabilities of drones and photogrammetric techniques, provides similar precision to LIDAR and Laser Scanning, and has recently been used in river geomorphology, although the model sensitivity to the altimetric and planimetric control benchmarks has not been fully explained. This study is aimed to analyze the potential of SfM in obtaining bathymetric data of ephemeral rivers in the coastal area of Peru. To this end, the technique was applied to the Rimac River, which runs across the Peru’s capital, Lima. Field measurements consisted on: a cross section survey along a 1.1 km-length stretch of the Rimac River, placement of five benchmarks along of the river banks (i.e. control points, CP), and collecting 780 aerial photographs using drones (Phantom 2 Vision + series). Subsequently, the photographs were processed and by using the SfM technique, a dense cloud point was obtained, and then the model was calibrated using the CPs. A sensitivity analysis of the model towards the density of CPs suggests that the maximum mean error, which are located at the margins of the study stretch, is ~ 0.29 m the CPs average spacement is around 5B (B=xxxx m is the channel width). Likewise, after applying the optical bathymetric mapping interpolation scheme to both the subaerial and subaquatic domain, a 0.5m resolution digital elevation model was obtained.
Our results suggest that the application of SfM in a cost effective technique that has the potential to provide actionable bathymetric data from ephemeral rivers in Peru, and possibly to other developing countries.
Key words: Structure-from-motion, drones, river bathymetry.