Network Design and Quality Checks in Automatic Orientation of Close-Range Photogrammetric Blocks

Abstract

Due to the recent improvements of automatic measurement procedures in photogrammetry, multi-view 3D reconstruction technologies are becoming a favourite survey tool. Rapidly widening structure-from-motion (SfM) software packages offer significantly easier image processing workflows than traditional photogrammetry packages. However, while most orientation and surface reconstruction strategies will almost always succeed in any given task, estimating the quality of the result is, to some extent, still an open issue. An assessment of the precision and reliability of block orientation is necessary and should be included in every processing pipeline. Such a need was clearly felt from the results of close-range photogrammetric surveys of in situ full-scale and laboratory-scale experiments. In order to study the impact of the block control and the camera network design on the block orientation accuracy, a series of Monte Carlo simulations was performed. Two image block configurations were investigated: a single pseudo-normal strip and a circular highly-convergent block. The influence of surveying and data processing choices, such as the number and accuracy of the ground control points, autofocus and camera calibration was investigated. The research highlights the most significant aspects and processes to be taken into account for adequate in situ and laboratory surveys, when modern SfM software packages are used, and evaluates their effect on the quality of the results of the surface reconstruction.

Combination of UAV and terrestrial photogrammetry to assess rapid glacier evolution and map glacier hazards

“…Point density partly depends upon the surveying technique used, since it is controlled by the distance between sensor and surface, and determines spatial resolution. In SfM photogrammetry, point density is affected by image texture, sharpness and resolution, which influence the performance of dense matching algorithms (Dall'Asta et al, 2015), while in TLS it can be set up as a data acquisition input parameter. In this study, the number of neighbors N (inside a sphere of radius R = 1 m) divided by the neighborhood surface was used to evaluate the local point density D in CloudCompare (http://www.…”

THE INFLUENCE OF FLIGHT PLANNING AND CAMERA ORIENTATION IN UAVs PHOTOGRAMMETRY. A TEST IN THE AREA OF ROCCA SAN SILVESTRO (LI), TUSCANY

“…Are all these points necessary to ensure an accurate georeferencing of the model or the minimum number of points to be used is related with the number and/or type of images? To evaluate this factor another short test was performed as well, according to some interesting consideration that are reported in several papers that deal with the photogrammetric simulation using robust statistical approach (Dall'Asta et al, 2015;Hastedt, 2004;Luhmann, 2011) According to this assumption, the attention was focused on two projects, selected on the base of the results of the research presented in this paper. The idea of evaluate the impact of the camera and flight configuration also on the accuracy of the bundle block adjustment of the projects is a second step of research.…”

Open Source and Independent Methods for Bundle Adjustment Assessment in Close-Range UAV Photogrammetry

“…This has been applied, for example, to help camera self-calibration using the extended collinearity equations to converge by only using the Exif values of the images [41,47]. Furthermore, DBAT has been tested to reprocess real-world datasets, such as a small sample of large-format aerial images [21] and close-range photogrammetry projects, both terrestrial and UAV-based [22,48]. DBAT provides comprehensive statistics, such as posterior standard deviations of exterior and interior parameters, intersecting angles between images, sigma naught, correlations between the computed parameters, etc.…”