scholarly journals 3-D uncertainty-based topographic change detection with structure-from-motion photogrammetry: precision maps for ground control and directly georeferenced surveys

2017 ◽  
Vol 42 (12) ◽  
pp. 1769-1788 ◽  
Author(s):  
Mike R. James ◽  
Stuart Robson ◽  
Mark W. Smith
Keyword(s):  
Change Detection ◽  
Structure From Motion ◽  
Ground Control

scholarly journals Short Communication: Optimizing UAV-SfM based topographic change detection with survey co-alignment

2020 ◽  
Author(s):  
Tjalling de Haas ◽  
Wiebe Nijland ◽  
Brian W. McArdell ◽  
Maurice W. M. L. Kalthof
Keyword(s):  
Change Detection ◽  
Unmanned Aerial Vehicles ◽  
Structure From Motion ◽  
Short Communication ◽  
Swiss Alps ◽  
Ground Control ◽  
Control Points ◽  
Classical Approach ◽  
Ground Control Points ◽  
Surface Models

Abstract. High-quality digital surface models (DSMs) generated from structure-from-motion (SfM) based on imagery captured from unmanned aerial vehicles (UAVs), are increasingly used for topographic change detection. Classically, DSMs were generated for each survey individually and then compared to quantify topographic change, but recently it was shown that co-aligning the images of multiple surveys may enhance the accuracy of topographic change detection. Here, we use nine surveys over the Illgraben debris-flow torrent in the Swiss Alps to compare the accuracy of three approaches for UAV-SfM topographic change detection: (1) the classical approach where each survey is processed individually using ground control points (GCPs), (2) co-alignment of all surveys without GCPs, and (3) co-alignment of all surveys with GCPs. We demonstrate that compared to the classical approach co-alignment enhances the accuracy of topographic change detection by a factor 4 with GCPs and a factor 3 without GCPs, leading to xy and z offsets

scholarly journals Case Report: Optimization of Topographic Change Detection With UAV Structure-From-Motion Photogrammetry Through Survey Co-Alignment

2021 ◽  
Vol 2 ◽  
Author(s):  
Tjalling de Haas ◽  
Wiebe Nijland ◽  
Brian W. McArdell ◽  
Maurice W. M. L. Kalthof
Keyword(s):  
Change Detection ◽  
Structure From Motion ◽  
Swiss Alps ◽  
Ground Control ◽  
Control Points ◽  
Classical Approach ◽  
Absolute Accuracy ◽  
Ground Control Points ◽  
Surface Models ◽  
A Minor

High-quality digital surface models (DSMs) generated from structure-from-motion (SfM) based on imagery captured from unmanned aerial vehicles (UAVs), are increasingly used for topographic change detection. Classically, DSMs were generated for each survey individually and then compared to quantify topographic change, but recently it was shown that co-aligning the images of multiple surveys may enhance the accuracy of topographic change detection. Here, we use nine surveys over the Illgraben debris-flow torrent in the Swiss Alps to compare the accuracy of three approaches for UAV-SfM topographic change detection: 1) the classical approach where each survey is processed individually using ground control points (GCPs), 2) co-alignment of all surveys without GCPs, and 3) co-alignment of all surveys with GCPs. We demonstrate that compared to the classical approach co-alignment with GCPs leads to a minor and marginally significant increase in absolute accuracy. Moreover, compared to the classical approach co-alignment enhances the relative accuracy of topographic change detection by a factor 4 with GCPs and a factor 3 without GCPs, leading to xy and z offsets <0.1 m for both co-alignment approaches. We further show that co-alignment leads to particularly large improvements in the accuracy of poorly aligned surveys that have severe offsets when processed individually, by forcing them onto the more accurate common geometry set by the other surveys. Based on these results we advocate that co-alignment, preferably with GCPs to ensure a high absolute accuracy, should become common-practice in high-accuracy UAV-SfM topographic change detection studies for projects with sufficient stable areas.

scholarly journals A New Fast and Low-Cost Photogrammetry Method for the Engineering Characterization of Rock Slopes

2019 ◽  
Vol 11 (11) ◽  
pp. 1267 ◽  
Author(s):  
Francioni ◽  
Simone ◽  
Stead ◽  
Sciarra ◽  
Mataloni ◽  
...  
Keyword(s):  
Structure From Motion ◽  
Engineering Geology ◽  
Survey Methods ◽  
Digital Camera ◽  
3D Models ◽  
Ground Control ◽  
Control Points ◽  
Digital Photogrammetry ◽  
Ground Control Points ◽  
The Creation

Digital photogrammetry (DP) represents one of the most used survey techniques in engineering geology. The availability of new high-resolution digital cameras and photogrammetry software has led to a step-change increase in the quality of engineering and structural geological data that can be collected. In particular, the introduction of the structure from motion methodology has led to a significant increase in the routine uses of photogrammetry in geological and engineering geological practice, making this method of survey easier and more attractive. Using structure from motion methods, the creation of photogrammetric 3D models is now easier and faster, however the use of ground control points to scale/geo-reference the models are still required. This often leads to the necessity of using total stations or Global Positioning System (GPS) for the acquisition of ground control points. Although the integrated use of digital photogrammetry and total station/GPS is now common practice, it is clear that this may not always be practical or economically convenient due to the increase in cost of the survey. To address these issues, this research proposes a new method of utilizing photogrammetry for the creation of georeferenced and scaled 3D models not requiring the use of total stations and GPS. The method is based on the use of an object of known geometry located on the outcrop during the survey. Targets located on such objects are used as ground control points and their coordinates are calculated using a simple geological compass and trigonometric formula or CAD 3D software. We present three different levels of survey using (i) a calibrated digital camera, (ii) a non-calibrated digital camera and (iii) two commercial smartphones. The data obtained using the proposed approach and the three levels of survey methods have been validated against a laser scanning (LS) point cloud. Through this validation we highlight the advantages and limitations of the proposed method, suggesting potential applications in engineering geology.

scholarly journals Evaluating the potential of post-processing kinematic (PPK) georeferencing for UAV-based structure- from-motion (SfM) photogrammetry and surface change detection

2019 ◽  
Vol 7 (3) ◽  
pp. 807-827 ◽  
Author(s):  
He Zhang ◽  
Emilien Aldana-Jague ◽  
François Clapuyt ◽  
Florian Wilken ◽  
Veerle Vanacker ◽  
...  
Keyword(s):  
Change Detection ◽  
Structure From Motion ◽  
Low Cost ◽  
Post Processing ◽  
Positional Accuracy ◽  
Surface Change ◽  
Ground Control Points ◽  
Single Lens ◽  
Surface Representations ◽  
Uav Images

Abstract. Images captured by unmanned aerial vehicles (UAVs) and processed by structure-from-motion (SfM) photogrammetry are increasingly used in geomorphology to obtain high-resolution topography data. Conventional georeferencing using ground control points (GCPs) provides reliable positioning, but the geometrical accuracy critically depends on the number and spatial layout of the GCPs. This limits the time and cost effectiveness. Direct georeferencing of the UAV images with differential GNSS, such as PPK (post-processing kinematic), may overcome these limitations by providing accurate and directly georeferenced surveys. To investigate the positional accuracy, repeatability and reproducibility of digital surface models (DSMs) generated by a UAV–PPK–SfM workflow, we carried out multiple flight missions with two different camera–UAV systems: a small-form low-cost micro-UAV equipped with a high field of view (FOV) action camera and a professional UAV equipped with a digital single lens reflex (DSLR) camera. Our analysis showed that the PPK solution provides the same accuracy (MAE: ca. 0.02 m, RMSE: ca. 0.03 m) as the GCP method for both UAV systems. Our study demonstrated that a UAV–PPK–SfM workflow can provide consistent, repeatable 4-D data with an accuracy of a few centimeters. However, a few flights showed vertical bias and this could be corrected using one single GCP. We further evaluated different methods to estimate DSM uncertainty and show that this has a large impact on centimeter-level topographical change detection. The DSM reconstruction and surface change detection based on a DSLR and action camera were reproducible: the main difference lies in the level of detail of the surface representations. The PPK–SfM workflow in the context of 4-D Earth surface monitoring should be considered an efficient tool to monitor geomorphic processes accurately and quickly at a very high spatial and temporal resolution.

Combined aerial and ground-based Structure-from-Motion modelling for a vertical rock wall face to estimate volume of failure

2020 ◽  
Author(s):  
Helge Smebye
Keyword(s):  
High Resolution ◽  
Structure From Motion ◽  
Software Package ◽  
Standoff Distance ◽  
Ground Control ◽  
Surface Model ◽  
Digital Surface Model ◽  
Failure Model ◽  
Volume Estimate ◽  
Rock Wall

<p>Combined aerial and ground-based Structure-from-Motion modelling for a vertical rock wall face to estimate volume of failure</p><p> </p><p>Helge C. Smebye,<sup>a,* </sup>Sean E. Salazar,<sup>a</sup> Asgeir O. K. Lysdahl,<sup>a</sup></p><p>aNorwegian Geotechnical Institute, Sognsveien 72, 0855 Oslo, Norway</p><p> </p><p><strong>Abstract</strong>.  The A rock wall failure occurred along a major highway in south-eastern Norway, shutting down two lanes of traffic for an extended period of time while the road authority inspected and repaired the wall. It was desired to have a high-resolution digital surface model along a 215-m long section of the 34-m tall vertical rock wall that included the failure zone.</p><p>A Structure-from-Motion (SfM)-based methodology was selected to achieve the desired resolution on the rock wall face, as well as below the foot and above the head of the wall. Due to the proximity of the wall face to the remaining open lanes of traffic, it was not possible to survey the face of the wall using a remotely piloted aircraft system (RPAS). Therefore, a combined platform photogrammetric surveying technique was employed to ensure optimal photographic coverage and to generate the best possible model. Ground control points (GCP) were distributed and surveyed along the bottom and top of the wall and an RPAS was flown manually over the head of the wall to capture downward facing (nadir) images. A lift crane was also employed to capture images from elevations varying between 20–30 meters with a standoff distance of 15 meters from the wall. Finally, ground-based images were captured using a camera equipped with real-time GNSS from the top of the opposite rock wall (across the highway) with standoff distance of approximately 65 meters.</p><p>In total, over 800 images were ingested into a commercial SfM software package. The bundle adjustments were assisted by the GNSS-equipped camera locations and the surveyed GCP were imported to georeference the resulting model. The dense point cloud product was exported to a separate meshing software package for comparison with a second dense surface model that was derived from pre-existing images of the as-built condition of same rock wall face (prior to failure). By subtracting the post-failure model from the pre-failure model, a volume estimate of the material, that was mobilized during the failure, was determined.</p><p>The utility of the multi-platform survey technique was demonstrated. The combination of aerial and ground-based photographic surveying techniques provided optimal photographic coverage of the entire length of the rock wall to successfully derive high-resolution surface models and volume estimates.</p><p> </p><p><strong> </strong></p><p><strong>Keywords</strong>: Structure-from-Motion, photogrammetry, digital surface model, natural hazards, ground control.</p><p> </p><p><strong>*</strong>Helge C. Smebye, E-mail: [email protected]</p>

scholarly journals Geomorphic Change Detection Using Cost-Effective Structure-from-Motion Photogrammetry: Evaluation of Direct Georeferencing from Consumer-Grade UAS at Orewa Beach (New Zealand)

2020 ◽  
Vol 86 (5) ◽  
pp. 289-298 ◽  
Author(s):  
Stephane Bertin ◽  
Benjamin Levy ◽  
Trevor Gee ◽  
Patrice Delmas
Keyword(s):  
New Zealand ◽  
Change Detection ◽  
Structure From Motion ◽  
Cost Effective ◽  
Satellite System ◽  
Unmanned Aerial Systems ◽  
Control Points ◽  
Measurement Quality ◽  
Graphic Data ◽  
Improve Measurement

Unmanned aerial systems (UAS) and structure-from-motion photogrammetry are transforming the way we produce topo- graphic data, with applications covering many disciplines in the geosciences, including coastal studies. To overcome limitations of ground control points (GCPs), we evaluate direct georeferencing (DG) of consumer UAS imagery for the cost-effective measurement of beach topography. Using DG, camera positions determined with on-board instruments provide air control points for photogrammetry, obviating the need for presurveyed GCPs. We validate the approach at Orewa Beach, New Zealand, achieving vertical accuracies similar to light detection and ranging (< 0.2 m) at a higher resolution (< 0.1 m). A low-quality global navigation satellite system onboard a consumer UAS remains the main constraint on measurement quality. We show how independent topo- graphic data sets, which are increasingly available world- wide, can improve measurement quality, and hence change detection capacity. Our understanding of measurement quality achieved in this study is applied to the assessment of morphological and volumetric change at Orewa Beach.

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