@misc{74933, type = "Article", year = "2019", title = "UAV survey of a coastal cliff face - Selection of the best imaging angle", journal = "Measurement", editor = "Elsevier Sci Ltd", volume = "139", number = "", pages = "10-20", author = "Jaud Marion, Letortu Pauline, Thery Claire, Grandjean Philippe, Costa Stephane, Maquaire Olivier, Davidson Robert, Le Dantec Nicolas", url = "", organization = "", address = "FRANCE", doi = "https://doi.org/10.1016/j.measurement.2019.02.024", abstract = "
UAVs are relevant for monitoring cliff faces. In this study, several flights are performed with various imaging angles (nadir, 20 degrees, 30 degrees and 40 degrees off-nadir) to assess the impact of the imaging angle on the 3D cliff face reconstruction. Occlusions issues arising with sub-vertical cliffs make nadir surveys nearly irrelevant. The results obtained with 20 degrees, 30 degrees and 40 degrees off-nadir imaging angles are satisfactory regarding texture restitution and accuracy with respectively 5.5 cm, 5.9 cm and 4.9 cm of error, higher tilting angles yielding better reconstructions on sub-vertical or overhanging parts of the cliff. This article also investigates other parameters affecting tiepoint detection on the cliff face, as the effective overlap, the UAV-cliff face distance and the cliff face illumination. Guidelines are provided for UAV survey parameterization, aiming at capturing the whole cliff face with a good trade-off between distance to the cliff, flight height and spatial resolution of the photographs.
", key = "" }