Modelling Steep Surfaces by Various Configurations of Nadir and Oblique Photogrammetry

Abstract

Commission I, ICWG I/VbKEY WORDS: Photogrammetry, UAS, Sandpit, Point Cloud, Analysis, Assessment ABSTRACT:Among the parts of the territory requiring periodical and careful monitoring, many have steep surfaces: quarries, river basins, landslides, dangerous mountainsides. Aerial photogrammetry based on lightweight unmanned aircraft systems (UAS) is rapidly becoming the tool of election to survey limited areas of land with a high level of detail. Aerial photogrammetry is traditionally based on vertical images and only recently the use of significantly inclined imagery has been considered. Oblique photogrammetry presents peculiar aspects and offers improved capabilities for steep surface reconstruction. Full comprehension of oblique photogrammetry still requires research efforts and the evaluation of diverse case studies. In the present paper, the focus is on the photogrammetric UAS-based survey of a part of a large sandpit. Various flight configurations are considered: ordinary linear strips, radial strips (as the scarp considered has a semi-circular shape) and curved ones; moreover, nadir looking and oblique image blocks were acquired. Around 300 control points were measured with a topographic total station. The various datasets considered are evaluated in terms of density of the extracted point cloud and in terms of the distance between the reconstructed surface and a number of check points.

How Image Acquisition Geometry of UAV Campaigns Affects the Derived Products and Their Accuracy in Areas with Complex Geomorphology

“…However, it was also demonstrated that nadir orientation images along with a dense distribution of ground control points (GCPs) exhibited similar accuracy, which is even comparable to the one obtained from a terrestrial laser scanner [21]. In addition, various datasets including different configurations of nadir-oblique imagery were evaluated in terms of point cloud density and accuracy and showed no significant differences [22]. Nadir and off-nadir images were evaluated for high-resolution topography, presenting an accuracy of a few centimeters [23].…”

3D Scanning: A Comprehensive Survey

“…1) Steep Surfaces: Regularly monitoring the boundaries of a territory including steep surfaces, e.g. mountainsides, quarries, landslides or river basins, is amongst the important applications of aerial photogrammetry, which can be achieved with a decent level of details using lightweight UASs, having recently led to higher-quality results taking advantage of inclined images under oblique photogrammetry frameworks, rather than relying on strictly vertical images [74]. In the latter study, a large sandpit has been considered as a casestudy, with linear, radial and semi-circular strips as different flight configurations, where 300 control points were captured using a topographic TS.…”

Investigating the length, area and volume measurement accuracy of UAV-Based oblique photogrammetry models produced with and without ground control points

“…Chudley et al [19] called "Highaccuracy UAV photogrammetry of ice sheet dynamics with no ground control points", the application of an alternative SFM-MVS (structure from motion-multi-view stereo) geolocation method called GNSS-supported aerial triangulation was presented; in this method, a carrier-phase GNSS receiver located onboard georeferences the SFM-MVS point cloud, significantly reducing the need for GCPs. Considering various flight configurations such as linear strips, radial strips and curved strips, the diverse obtained datasets were evaluated in terms of the density of the extracted point clouds and the distance between the reconstructed surface and control points [20].…”