Diachronic UAV Photogrammetry of a Sandy Beach in Brittany (France) for a Long-Term Coastal Observatory

Abstract

In the dual context of coastal hazard intensification and the growing number of stakes exposed to these hazards, coastal observatories are in demand to provide a structured framework dedicated to long-term monitoring. This article describes the drone-based photogrammetry monitoring performed since 2006 on Porsmilin Beach (Brittany, France) in the framework of the DYNALIT (Littoral and Coastline Dynamics) observatory, focusing on data quality and the consistency of long-term time series under the influence of multiple technological evolutions: Unmanned Aerial Vehicles (UAV) platforms with the arrival of electric multirotor drones, processing tools with the development of structure-from-motion (SfM) photogrammetry, and operational modes of survey. A study case is presented to show the potential of UAV monitoring to study storm impacts and beach resilience. The relevance of high-accuracy monitoring is also highlighted. With the current method, an accuracy of 3 cm can be achieved on the digital elevation model (DEM) and the orthophotograph. The question of the representativity and frequency of DEM time points is raised.

RTK GNSS-Assisted Terrestrial SfM Photogrammetry without GCP: Application to Coastal Morphodynamics Monitoring

“…To the east and west, it is flanked by orthogneiss cliffs of about 20 m high and bounded by headlands and bedrocks. Porsmilin beach has been regularly monitored since 2003 with monthly measurements of topographical cross-shore profiles, being completed by Digital Elevation Models (DEM) computed from UAV photographs since 2006 and from Terrestrial Laser Scanner (TLS) point clouds since 2009 [3,27].…”

“…Two kinds of surveys can be distinguished: aerial surveys and terrestrial surveys. Aerial surveys are generally performed by Unmanned Aerial Vehicles (UAVs) and mainly used for beach surveys [1][2][3], whereas data collected from a terrestrial point of view are more suited to cliff surveys, allowing for better capturing the cliff face. These terrestrial data are typically obtained using a Terrestrial Laser Scanner (TLS) [4,5], a Mobile Laser Scanner (MLS) [6,7], or terrestrial photogrammetry [8,9].…”

Potential of Smartphone SfM Photogrammetry to Measure Coastal Morphodynamics

“…This site has been chosen for the tests because it is monitored in the framework of the national DYNALIT (Littoral and Coastline Dynamics) observatory [14]. In this context, a TLS survey was carried out simultaneously to the smartphone SfM photogrammetry survey.…”

The Influence of Flight Configuration, Camera Calibration, and Ground Control Points for Digital Terrain Model and Orthomosaic Generation Using Unmanned Aerial Vehicles Imagery

“…Basically, UAVs applications can be classified as forestry (Dandois, Olano and Ellis, 2015), agriculture (Kitano et al, 2019;Oliveira et al, 2018), archaeology and cultural heritage (Tombari and Remondino, 2013), environmental survey (Jaud et al, 2019), and civil engineering (Greenwood, Lynch and Zekkos, 2019). Among the reasons for this spread in the civil engineering community is due to the possibility of generating digital cartography products faster and at a lower cost when compared to conventional surveying, traditional aerial Photogrammetry and orbital remote sensing (Colomina and Molina, 2014).…”