scholarly journals Optimising UAV topographic surveys processed with structure-from-motion: Ground control quality, quantity and bundle adjustment

Geomorphology ◽  
2017 ◽  
Vol 280 ◽  
pp. 51-66 ◽  
Author(s):  
M.R. James ◽  
S. Robson ◽  
S. d'Oleire-Oltmanns ◽  
U. Niethammer
Keyword(s):  
Structure From Motion ◽  
Bundle Adjustment ◽  
Ground Control ◽  
Control Quality ◽  
Topographic Surveys

scholarly journals PRECISION OF VISUAL LOCALIZATION USING DYNAMIC GROUND CONTROL POINTS

2020 ◽  
Vol XLIII-B1-2020 ◽  
pp. 363-370
Author(s):  
P. Trusheim ◽  
C. Heipke
Keyword(s):  
Rapid Development ◽  
Sliding Window ◽  
Bundle Adjustment ◽  
Ground Control ◽  
Visual Localization ◽  
Control Points ◽  
Automated Driving ◽  
Sliding Windows ◽  
Ground Control Points

Abstract. Localization is one of the first steps in navigation. Especially due to the rapid development in automated driving, a precise and reliable localization becomes essential. In this paper, we report an investigation of the usage of dynamic ground control points (GCP) in visual localization in an automotive environment. Instead of having fixed positions, dynamic GCPs move together with the camera. As a measure of quality, we employ the precision of the bundle adjustment results. In our experiments, we simulate and investigate different realistic traffic scenarios. After investigating the role of tie points, we compare an approach using dynamic GCPs to an approach with static GCPs to answer the question how a comparable precision can be reached for visual localization. We show, that in our scenario, where two dynamic GCPs move together with a camera, similar results are indeed obtained to using a number of static GCPs distributed over the whole trajectory. In another experiment, we take a closer look at sliding window bundle adjustments. Sliding windows make it possible to work with an arbitrarily large number of images and to still obtain near real-time results. We investigate this approach in combination with dynamic GCPs and vary the no. of images per window.

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.

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>

Refraction-Based Bundle Adjustment for Scale Reconstructible Structure from Motion

2018 ◽  
Vol 30 (4) ◽  
pp. 660-670 ◽  
Author(s):  
Akira Shibata ◽  
Yukari Okumura ◽  
Hiromitsu Fujii ◽  
Atsushi Yamashita ◽  
Hajime Asama ◽  
...  
Keyword(s):  
3D Reconstruction ◽  
Structure From Motion ◽  
Error Function ◽  
Bundle Adjustment ◽  
Reconstruction Method ◽  
Actual Measurement ◽  
3D Measurements ◽  
Absolute Scale ◽  
The Absolute ◽  
Motion Method

Structure from motion is a three-dimensional (3D) reconstruction method that uses one camera. However, the absolute scale of objects cannot be reconstructed by the conventional structure from motion method. In our previous studies, to solve this problem by using refraction, we proposed a scale reconstructible structure from motion method. In our measurement system, a refractive plate is fixed in front of a camera and images are captured through this plate. To overcome the geometrical constraints, we derived an extended essential equation by theoretically considering the effect of refraction. By applying this formula to 3D measurements, the absolute scale of an object could be obtained. However, this method was verified only by a simulation under ideal conditions, for example, by not taking into account real phenomena such as noise or occlusion, which are necessarily caused in actual measurements. In this study, to robustly apply this method to an actual measurement with real images, we introduced a novel bundle adjustment method based on the refraction effect. This optimization technique can reduce the 3D reconstruction errors caused by measurement noise in actual scenes. In particular, we propose a new error function considering the effect of refraction. By minimizing the value of this error function, accurate 3D reconstruction results can be obtained. To evaluate the effectiveness of the proposed method, experiments using both simulations and real images were conducted. The results of the simulation show that the proposed method is theoretically accurate. The results of the experiments using real images show that the proposed method is effective for real 3D measurements.

scholarly journals Structural analysis of clastic dikes based on Structure from Motion/Multi-View Stereo

2018 ◽  
Author(s):  
Carlos H Grohmann ◽  
Camila D Viana ◽  
Mariana TS Busarello ◽  
Guilherme PB Garcia
Keyword(s):  
Structural Analysis ◽  
Structure From Motion ◽  
Low Cost ◽  
Three Dimensional ◽  
Fine Sand ◽  
Bundle Adjustment ◽  
Three Dimensional Model ◽  
Focal Distance ◽  
Camera Orientation ◽  
Camera Position

This work presents the development of a three-dimensional model of an outcrop of the Corumbataí Formation using Structure from Motion and Multi-View Stereo (SfM-MVS) techniques in order to provide a structural analysis of clastic dikes cutting through siltstone layers. Composed mainly of fine sand and silt, these dikes are formed by sand intrusions when a wet sandy layer is affected by earthquakes of at least 6.5 magnitude, being used as a record of such events.While traditional photogrammetry requires the user to input a series of parameters related to the camera orientation and its characteristics (such as focal distance), in SfM-MVS the scene geometry, camera position and orientations are automatically determined by a bundle adjustment, an iterative procedure based on a set of overlapping images. It is considered a low-cost technique in both hardware and software, also being able to provide point density and accuracy on par to the ones obtained with terrestrial laser scanner.The results acquired on this research have a good agreement with previous works, yielding a NNW main orientation for the dikes measured in the field and on the 3D model. The development of this work showed that SfM-MVS use and practice on geosciences still needs more studies on the optimization of the involved parameters (such as camera orientation, image overlap and angle of illumination), which, when accomplished, will result in less processing time and more accurate models.

scholarly journals AUTOMATIC KAPPA ANGLE ESTIMATION FOR AIR PHOTOS BASED ON PHASE ONLY CORRELATION

2016 ◽  
Vol XLI-B3 ◽  
pp. 131-135
Author(s):  
Z. Xiong ◽  
D. Stanley ◽  
Y. Xin
Keyword(s):  
Bundle Adjustment ◽  
Ground Control ◽  
Correlation Technique ◽  
Control Points ◽  
Initial Value ◽  
Ground Control Points ◽  
Attitude Angle ◽  
Camera Position ◽  
Air Photo ◽  
Orientation Parameters

The approximate value of exterior orientation parameters is needed for air photo bundle adjustment. Usually the air borne GPS/IMU can provide the initial value for the camera position and attitude angle. However, in some cases, the camera’s attitude angle is not available due to lack of IMU or other reasons. In this case, the kappa angle needs to be estimated for each photo before bundle adjustment. The kappa angle can be obtained from the Ground Control Points (GCPs) in the photo. Unfortunately it is not the case that enough GCPs are always available. In order to overcome this problem, an algorithm is developed to automatically estimate the kappa angle for air photos based on phase only correlation technique. This function has been embedded in PCI software. Extensive experiments show that this algorithm is fast, reliable, and stable.

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