Use of UAV-Photogrammetry for Quasi-Vertical Wall Surveying

Abstract

In this study, an analysis of the capabilities of unmanned aerial vehicle (UAV) photogrammetry to obtain point clouds from areas with a near-vertical inclination was carried out. For this purpose, 18 different combinations were proposed, varying the number of ground control points (GCPs), the adequacy (or not) of the distribution of GCPs, and the orientation of the photographs (nadir and oblique). The results have shown that under certain conditions, the accuracy achieved was similar to those obtained by a terrestrial laser scanner (TLS). For this reason, it is necessary to increase the number of GCPs as much as possible in order to cover a whole study area. In the event that this is not possible, the inclusion of oblique photography ostensibly improves results; therefore, it is always advisable since they also improve the geometric descriptions of break lines or sudden changes in slope. In this sense, UAVs seem to be a more economic substitute compared to TLS for vertical wall surveying.

Combining Nadir, Oblique, and Façade Imagery Enhances Reconstruction of Rock Formations Using Unmanned Aerial Vehicles

“…Based on the results presented here, it is advised to use the combination of nadir, oblique, and façade images to prevent high topographic errors--especially when façade information is needed, e.g., for producing high-quality texture layers for the rendering of 3-D models suited for visual assessment or classification of features on steep or vertical rock walls, or if the geometric accuracy of façades is important, e.g., for slope stability assessment. Similar findings were also suggested in the survey of a dam when GCP distribution was inadequate [34].…”

“…Circular scanning of sites, with the normal vectors of camera positions converging to a pseudopoint, is a common strategy for UAV-based collection of oblique images from near-vertical objects [33]. Martínez-Carricondo et al [34] used the combination of nadir and oblique images to improve the accuracy of topographic data from a vertical wall in the condition of inadequate GCP distribution. Such findings indicate the potential to improve the topographic accuracy and data completeness through combining UAV imagery acquired from various viewing perspectives, especially in complex terrain containing vertical surfaces.…”

Editorial for Special Issue “UAV Photogrammetry and Remote Sensing”

“…UAV Photogrammetry can model terrain surfaces with extreme or quasi-vertical morphologies [5]. In this work, several combinations of number of GCP, distribution and image orientation were tested in a dam belonging to Spain's hydraulic heritage, located in the Almería province, obtaining similar results than terrestrial laser scanner TLS.…”

A New Adaptive Method for the Extraction of Steel Design Structures from an Integrated Point Cloud

“…The development of these sensors drives engineers and scientists to come up with newer measurement methods and associated applications. More and more of the above find their application in civil engineering [ 1 , 2 , 3 ], environmental engineering [ 4 , 5 , 6 ], construction [ 7 , 8 , 9 , 10 ] or architecture [ 11 , 12 ], thus intensively stimulating the further progress of these technologies.…”