Special Issue "Structure from Motion (SfM) Photogrammetry for Geomatics and Geoscience Applications"

A special issue of Remote Sensing (ISSN 2072-4292). This special issue belongs to the section "Remote Sensing Image Processing".

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editors

Prof. Dr. Antonio Vettore
E-Mail Website
Guest Editor
Interdepartmental Research Center of Geomatics (CIRGEO), University of Padova, via dell’Università 16, 35020 Legnaro (PD), Italy
Tel. +390498272688
Interests: mobile mapping systems, inertial navigation systems, road tracking, image processing; laser scanner applications and GPS/INS techniques for surveying and 3D modeling of cultural heritage sites; processing of LiDAR data from airborne or ground sensors (ALS & TLS), both discrete return and full waveform
Special Issues and Collections in MDPI journals
Dr. Andrea Masiero
E-Mail Website
Guest Editor
Secretary of ISPRS WG I/7 - Mobile Mapping Technology, Interdepartmental Research Center of Geomatics (CIRGEO), University of Padua, Italy
Interests: Geomatics; Mobile Mapping; Laser Scanning; Photogrammetry; Remote Sensing; Navigation; Data Processing; Machine Learning; Unmanned Aerial Vehicles; Cultural Heritage
Special Issues and Collections in MDPI journals
Prof. Dr. Ayman F. Habib
E-Mail Website
Guest Editor
Purdue University, Lyles School of Civil Engineering, 550 Stadium Mall Drive, HAMP 4108, West Lafayette, IN 47907, USA
Interests: Photogrammetry, Laser scanning, Mobile Mapping Systems, System Calibration, Computer Vision, Unmanned Aerial Mapping Systems, and Multi-Sensor/Multi-platform data integration
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Nowadays, a large number of applications require reliable geometric information about objects and the environment. The most commonly-used techniques for obtaining such 3D information without contact with the objects are usually LiDAR (Light Detection And Ranging) and photogrammetry. Despite both these techniques are widely used, and sometimes integrated together, two key factors are motivating the recent fast increase of photogrammetry usage: the availability of low cost cameras, which can easily mounted on UAVs (Unmanned Aerial Vehicles) and are commonly embedded in smartphones or other mobile devices, and to the recent introduction of almost automated software, typically based on the Structure from Motion approach, for easily obtaining tridimensional information from images.

The aim of this Special Issue is that of presenting new research advancements on methodological and algorithmic aspects on photogrammetry and Structure from Motion, on the integration of photogrammetric reconstruction with other systems, on the processing and analysis of image-based tridimensional data, and on the use of photogrammetry in applications related in particular to geomatics, geosciences, and related fields, such as surveying, mobile mapping, hydrology, geomorphology, civil engineering, architecture, cultural heritage, and precision farming.

Dr. Antonio Vettore

Dr. Andrea Masiero

Prof. Dr. Ayman F. Habib

Guest Editors

Manuscript Submission Information

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Keywords

  • Photogrammetry
  • Structure from Motion
  • Geoscience
  • Geomatics
  • UAV
  • 3D data processing
  • Mobile mapping
  • DTM
  • Remote Sensing
  • GIS

Published Papers (11 papers)

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Research

Open AccessArticle
Relative Importance of Binocular Disparity and Motion Parallax for Depth Estimation: A Computer Vision Approach
Remote Sens. 2019, 11(17), 1990; https://doi.org/10.3390/rs11171990 - 23 Aug 2019
Abstract
Binocular disparity and motion parallax are the most important cues for depth estimation in human and computer vision. Here, we present an experimental study to evaluate the accuracy of these two cues in depth estimation to stationary objects in a static environment. Depth [...] Read more.
Binocular disparity and motion parallax are the most important cues for depth estimation in human and computer vision. Here, we present an experimental study to evaluate the accuracy of these two cues in depth estimation to stationary objects in a static environment. Depth estimation via binocular disparity is most commonly implemented using stereo vision, which uses images from two or more cameras to triangulate and estimate distances. We use a commercial stereo camera mounted on a wheeled robot to create a depth map of the environment. The sequence of images obtained by one of these two cameras as well as the camera motion parameters serve as the input to our motion parallax-based depth estimation algorithm. The measured camera motion parameters include translational and angular velocities. Reference distance to the tracked features is provided by a LiDAR. Overall, our results show that at short distances stereo vision is more accurate, but at large distances the combination of parallax and camera motion provide better depth estimation. Therefore, by combining the two cues, one obtains depth estimation with greater range than is possible using either cue individually. Full article
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Open AccessArticle
New Strategies for Time Delay Estimation during System Calibration for UAV-Based GNSS/INS-Assisted Imaging Systems
Remote Sens. 2019, 11(15), 1811; https://doi.org/10.3390/rs11151811 - 01 Aug 2019
Abstract
The need for accurate 3D spatial information is growing rapidly in many of today’s key industries, such as precision agriculture, emergency management, infrastructure monitoring, and defense. Unmanned aerial vehicles (UAVs) equipped with global navigation satellite systems/inertial navigation systems (GNSS/INS) and consumer-grade digital imaging [...] Read more.
The need for accurate 3D spatial information is growing rapidly in many of today’s key industries, such as precision agriculture, emergency management, infrastructure monitoring, and defense. Unmanned aerial vehicles (UAVs) equipped with global navigation satellite systems/inertial navigation systems (GNSS/INS) and consumer-grade digital imaging sensors are capable of providing accurate 3D spatial information at a relatively low cost. However, with the use of consumer-grade sensors, system calibration is critical for accurate 3D reconstruction. In this study, ‘consumer-grade’ refers to cameras that require system calibration by the user instead of by the manufacturer or other high-end laboratory settings, as well as relatively low-cost GNSS/INS units. In addition to classical spatial system calibration, many consumer-grade sensors also need temporal calibration for accurate 3D reconstruction. This study examines the accuracy impact of time delay in the synchronization between the GNSS/INS unit and cameras on-board UAV-based mapping systems. After reviewing existing strategies, this study presents two approaches (direct and indirect) to correct for time delay between GNSS/INS recorded event markers and actual time of image exposure. Our results show that both approaches are capable of handling and correcting this time delay, with the direct approach being more rigorous. When a time delay exists and the direct or indirect approach is applied, horizontal accuracy of 1–3 times the ground sampling distance (GSD) can be achieved without either the use of any ground control points (GCPs) or adjusting the original GNSS/INS trajectory information. Full article
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Open AccessArticle
Indirect UAV Strip Georeferencing by On-Board GNSS Data under Poor Satellite Coverage
Remote Sens. 2019, 11(15), 1765; https://doi.org/10.3390/rs11151765 - 26 Jul 2019
Cited by 1
Abstract
The so-called Real Time Kinematic (RTK) option, which allows one to determine with cm-level accuracy the Unmanned Aerial Vehicles (UAV) camera position at shooting time, is also being made available on medium- or low-cost drones. It can be foreseen that a sizeable amount [...] Read more.
The so-called Real Time Kinematic (RTK) option, which allows one to determine with cm-level accuracy the Unmanned Aerial Vehicles (UAV) camera position at shooting time, is also being made available on medium- or low-cost drones. It can be foreseen that a sizeable amount of UAV surveys will be soon performed (almost) without Ground Control Points (GCP). However, obstacles to Global Navigation Satellite Systems (GNSS) signal at the optimal flight altitude might prevent accurate retrieval of camera station positions, e.g., in narrow gorges. In such cases, the master block can be georeferenced by tying it to an (auxiliary) block flown at higher altitude, where the GNSS signal is not impeded. To prove the point in a worst case scenario, but under controlled conditions, an experiment was devised. A single strip about 700 m long, surveyed by a multi-copter at 30 m relative flight height, was referenced with cm-level accuracy by joint adjustment with a block flown at 100 m relative flight height, acquired by a fixed-wing UAV provided with RTK option. The joint block orientation was repeated with or without GCP and with pre-calibrated or self-calibrated camera parameters. Accuracy on ground was assessed on a fair number of Check Points (CP). The results show that, even without GCP, the precision is effectively transferred from the auxiliary block projection centres to the object point horizontal coordinates and, with a pre-calibrated camera, also to the elevations. Full article
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Open AccessArticle
Modelling the Surface of Racing Vessel’s Hull by Laser Scanning and Digital Photogrammetry
Remote Sens. 2019, 11(13), 1526; https://doi.org/10.3390/rs11131526 - 27 Jun 2019
Abstract
The knowledge of the hull shape and geometry of a racing vessel is one of the most important factors for predicting boat performance. The Offshore Racing Congress (ORC) rating system specifies the calculation parameters of the hydrodynamic forces of boat lift and drag [...] Read more.
The knowledge of the hull shape and geometry of a racing vessel is one of the most important factors for predicting boat performance. The Offshore Racing Congress (ORC) rating system specifies the calculation parameters of the hydrodynamic forces of boat lift and drag on the basis of input data as the length of waterline while sailing, displacement, wetted surface and the volume distribution along the hull. It is represented by sophisticated calculations for national as well as international events and races. Measurement using a reflectorless total station in a coordinate system defined by the sailboat hull is the most established method approved by the ORC organisation. The determination of these geometric parameters by new, unconventional technologies, which should provide a quicker and more detailed measurement while preserving the quality and accuracy of results necessary for the handicap calculations was our main objective. Geometrical shapes of a cabin sailboat hull were determined by the technology of terrestrial laser scanning and two methods of digital close-range photogrammetry—convergence case of photogrammetry and Structure-from-Motion (SfM) method. High-Definition Surveying (HDS) targets for laser scanning and coded targets for digital photogrammetry were used throughout all methods in order to transform the resulting data into a single local coordinate system. The resulting models were mutually compared by visual, geometrical and statistical comparison. In conclusion, both technologies were considered suitable, however, with various advantages and disadvantages. Nevertheless, although labour intensive, the SfM photogrammetry can be considered the most suitable method if the correct procedures are followed. Full article
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Open AccessArticle
Monitoring and Computation of the Volumes of Stockpiles of Bulk Material by Means of UAV Photogrammetric Surveying
Remote Sens. 2019, 11(12), 1471; https://doi.org/10.3390/rs11121471 - 21 Jun 2019
Abstract
The monitoring and metric assessment of piles of natural or man-made materials plays a fundamental role in the production and management processes of multiple activities. Over time, the monitoring techniques have undergone an evolution linked to the progress of measure and data processing [...] Read more.
The monitoring and metric assessment of piles of natural or man-made materials plays a fundamental role in the production and management processes of multiple activities. Over time, the monitoring techniques have undergone an evolution linked to the progress of measure and data processing techniques; starting from classic topography to global navigation satellite system (GNSS) technologies up to the current survey systems like laser scanner and close-range photogrammetry. Last-generation 3D data management software allow for the processing of increasingly truer high-resolution 3D models. This study shows the results of a test for the monitoring and computing of stockpile volumes of material coming from the differentiated waste collection inserted in the recycling chain, performed by means of an unmanned aerial vehicle (UAV) photogrammetric survey and the generation of 3D models starting from point clouds. The test was carried out with two UAV flight sessions, with vertical and oblique camera configurations, and using a terrestrial laser scanner for measuring the ground control points and as ground truth for testing the two survey configurations. The computations of the volumes were carried out using two software and comparisons were made both with reference to the different survey configurations and to the computation software. Full article
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Open AccessArticle
A Fisheye Image Matching Method Boosted by Recursive Search Space for Close Range Photogrammetry
Remote Sens. 2019, 11(12), 1404; https://doi.org/10.3390/rs11121404 - 13 Jun 2019
Abstract
Close range photogrammetry (CRP) with large field-of-view images has become widespread in recent years, especially in terrestrial mobile mapping systems (TMMS). However, feature-based matching (FBM) with omnidirectional images (e.g., fisheye) is challenging even for state-of-the-art methods, such as the scale-invariant feature transform (SIFT), [...] Read more.
Close range photogrammetry (CRP) with large field-of-view images has become widespread in recent years, especially in terrestrial mobile mapping systems (TMMS). However, feature-based matching (FBM) with omnidirectional images (e.g., fisheye) is challenging even for state-of-the-art methods, such as the scale-invariant feature transform (SIFT), because of the strong scale change from image to image. This paper proposes an approach to boost FBM techniques on fisheye images with recursive reduction of the search space based on epipolar geometry. The epipolar restriction is calculated with the equidistant mathematical model and the initial exterior orientation parameters (EOPs) determined with navigation sensors from TMMS. The proposed method was assessed with data sets acquired by a low-cost TMMS. The TMMS is composed of a calibrated poly-dioptric system (Ricoh Theta S) and navigation sensors aimed at outdoor applications. The assessments show that Ricoh Theta S position and attitude were estimated in a global bundle adjustment with a precision (standard deviation) of 4 cm and 0.3°, respectively, using as observations the detected matches from the proposed method. Compared with other methods based on SIFT extended to the omnidirectional geometry, our approach achieved compatible results for outdoor applications. Full article
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Open AccessArticle
Corridor Mapping of Sandy Coastal Foredunes with UAS Photogrammetry and Mobile Laser Scanning
Remote Sens. 2019, 11(11), 1352; https://doi.org/10.3390/rs11111352 - 05 Jun 2019
Abstract
Recurrent monitoring of sandy beaches and of the dunes behind them is needed to improve the scientific knowledge on their dynamics as well as to develop sustainable management practices of those valuable landforms. Unmanned Aircraft Systems (UAS) are sought as a means to [...] Read more.
Recurrent monitoring of sandy beaches and of the dunes behind them is needed to improve the scientific knowledge on their dynamics as well as to develop sustainable management practices of those valuable landforms. Unmanned Aircraft Systems (UAS) are sought as a means to fulfill this need, especially leveraged by photogrammetric and LiDAR-based mapping methods and technology. The present study compares different strategies to carry UAS photogrammetric corridor mapping over linear extensions of sandy shores. In particular, we present results on the coupling of a UAS with a mobile laser scanning system, operating simultaneously in Cap Ferret, SW France. This aerial-terrestrial tandem enables terrain reconstruction with kinematic ground control points, thus largely avoiding the deployment of surveyed ground control points on the non-stable sandy ground. Results show how these three techniques—mobile laser scanning, photogrammetry based on ground control points, and photogrammetry based on kinematic ground control points—deliver accurate (i.e., root mean square errors < 15 cm) 3D reconstruction of beach-to-dune transition areas, the latter being performed at lower survey and logistic costs, and with enhanced spatial coverage capabilities. This study opens the gate for exploring longer (hundreds of kilometers) shoreline dynamics with ground-control-point-free air and ground mapping techniques. Full article
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Open AccessArticle
Mapping of River Terraces with Low-Cost UAS Based Structure-from-Motion Photogrammetry in a Complex Terrain Setting
Remote Sens. 2019, 11(4), 464; https://doi.org/10.3390/rs11040464 - 24 Feb 2019
Cited by 3
Abstract
River terraces are the principal geomorphic features for unraveling tectonics, sea level, and climate conditions during the evolutionary history of a river. The increasing availability of high-resolution topography data generated by low-cost Unmanned Aerial Systems (UAS) and modern photogrammetry offer an opportunity to [...] Read more.
River terraces are the principal geomorphic features for unraveling tectonics, sea level, and climate conditions during the evolutionary history of a river. The increasing availability of high-resolution topography data generated by low-cost Unmanned Aerial Systems (UAS) and modern photogrammetry offer an opportunity to identify and characterize these features. In this paper, we assessed the capabilities of UAS-based Structure-from-Motion (SfM) photogrammetry, coupled with a river terrace detection algorithm for mapping of river terraces over a 1.9 km2 valley of complex terrain setting, with a focus on the performance of this latest technology over such complex terrains. With the proposed image acquisition approach and SfM photogrammetry, we constructed a 3.8 cm resolution orthomosaic and digital surface model (DSM). The vertical accuracy of DSM was assessed against 196 independent checkpoints measured with a real-time kinematic (RTK) GPS. The results indicated that the root mean square error (RMSE) and mean absolute error (MAE) were 3.1 cm and 2.9 cm, respectively. These encouraging results suggest that this low-cost, logistically simple method can deliver high-quality terrain datasets even in the complex terrain, competitive with those obtained using more expensive laser scanning. A simple algorithm was then employed to detect river terraces from the generated DSM. The results showed that three levels of river terraces and a high-level floodplain were identified. Most of the detected river terraces were confirmed by field observations. Despite the highly erosive nature of fluvial systems, this work obtained good results, allowing fast analysis of fluvial valleys and their comparison. Overall, our results demonstrated that the low-cost UAS-based SfM technique could yield highly accurate ultrahigh-resolution topography data over complex terrain settings, making it particularly suitable for quick and cost-effective mapping of micro to medium-sized geomorphic features under such terrains in remote or poorly accessible areas. Methods discussed in this paper can also be applied to produce highly accurate digital terrain data over large spatial extents for some other places of complex terrains. Full article
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Open AccessFeature PaperArticle
Automated Aerial Triangulation for UAV-Based Mapping
Remote Sens. 2018, 10(12), 1952; https://doi.org/10.3390/rs10121952 - 04 Dec 2018
Cited by 6
Abstract
Accurate 3D reconstruction/modelling from unmanned aerial vehicle (UAV)-based imagery has become the key prerequisite in various applications. Although current commercial software has automated the process of image-based reconstruction, a transparent system, which can be incorporated with different user-defined constraints, is still preferred by [...] Read more.
Accurate 3D reconstruction/modelling from unmanned aerial vehicle (UAV)-based imagery has become the key prerequisite in various applications. Although current commercial software has automated the process of image-based reconstruction, a transparent system, which can be incorporated with different user-defined constraints, is still preferred by the photogrammetric research community. In this regard, this paper presents a transparent framework for the automated aerial triangulation of UAV images. The proposed framework is conducted in three steps. In the first step, two approaches, which take advantage of prior information regarding the flight trajectory, are implemented for reliable relative orientation recovery. Then, initial recovery of image exterior orientation parameters (EOPs) is achieved through either an incremental or global approach. Finally, a global bundle adjustment involving Ground Control Points (GCPs) and check points is carried out to refine all estimated parameters in the defined mapping coordinate system. Four real image datasets, which are acquired by two different UAV platforms, have been utilized to evaluate the feasibility of the proposed framework. In addition, a comparative analysis between the proposed framework and the existing commercial software is performed. The derived experimental results demonstrate the superior performance of the proposed framework in providing an accurate 3D model, especially when dealing with acquired UAV images containing repetitive pattern and significant image distortions. Full article
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Open AccessArticle
Accuracy of Unmanned Aerial Vehicle (UAV) and SfM Photogrammetry Survey as a Function of the Number and Location of Ground Control Points Used
Remote Sens. 2018, 10(10), 1606; https://doi.org/10.3390/rs10101606 - 09 Oct 2018
Cited by 16
Abstract
The geometrical accuracy of georeferenced digital surface models (DTM) obtained from images captured by micro-UAVs and processed by using structure from motion (SfM) photogrammetry depends on several factors, including flight design, camera quality, camera calibration, SfM algorithms and georeferencing strategy. This paper focusses [...] Read more.
The geometrical accuracy of georeferenced digital surface models (DTM) obtained from images captured by micro-UAVs and processed by using structure from motion (SfM) photogrammetry depends on several factors, including flight design, camera quality, camera calibration, SfM algorithms and georeferencing strategy. This paper focusses on the critical role of the number and location of ground control points (GCP) used during the georeferencing stage. A challenging case study involving an area of 1200+ ha, 100+ GCP and 2500+ photos was used. Three thousand, four hundred and sixty-five different combinations of control points were introduced in the bundle adjustment, whilst the accuracy of the model was evaluated using both control points and independent check points. The analysis demonstrates how much the accuracy improves as the number of GCP points increases, as well as the importance of an even distribution, how much the accuracy is overestimated when it is quantified only using control points rather than independent check points, and how the ground sample distance (GSD) of a project relates to the maximum accuracy that can be achieved. Full article
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Open AccessArticle
Efficient SfM for Oblique UAV Images: From Match Pair Selection to Geometrical Verification
Remote Sens. 2018, 10(8), 1246; https://doi.org/10.3390/rs10081246 - 08 Aug 2018
Cited by 5
Abstract
Accurate orientation is required for the applications of UAV (Unmanned Aerial Vehicle) images. In this study, an integrated Structure from Motion (SfM) solution is proposed, which aims to address three issues to ensure the efficient and reliable orientation of oblique UAV images, including [...] Read more.
Accurate orientation is required for the applications of UAV (Unmanned Aerial Vehicle) images. In this study, an integrated Structure from Motion (SfM) solution is proposed, which aims to address three issues to ensure the efficient and reliable orientation of oblique UAV images, including match pair selection for large-volume images with large overlap degree, reliable feature matching of images captured from varying directions, and efficient geometrical verification of initial matches. By using four datasets captured with different oblique imaging systems, the proposed SfM solution is comprehensively compared and analyzed. The results demonstrate that linear computational costs can be achieved in feature extraction and matching; although high decrease ratios occur in image pairs, reliable orientation results are still obtained from both the relative and absolute bundle adjustment (BA) tests when compared with other software packages. For the orientation of oblique UAV images, the proposed method can be an efficient and reliable solution. Full article
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