Article

Taking Computer Vision Aloft – Archaeological Three-dimensional Reconstructions from Aerial Photographs with PhotoScan

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Abstract

Structure from motion (SFM) algorithms are known for their ability to reconstruct a sparse point cloud of scenes that were imaged by a series of overlapping photographs. When complemented by stereo-matching algorithms, detailed three-dimensional models can be built from such photograph collections in a fully automated way. Since 2010, a computer vision software package called PhotoScan has been available from the Russian manufacturer AgiSoft LLC. Even though the programme has a straightforward and simple interface, state-of-the-art SFM and other computer vision algorithms are implemented that enable PhotoScan to generate very dense and accurate three-dimensional meshes of various (archaeological) settings captured in two-dimensional imagery. Using a mixture of archaeological case studies, it will be shown that this low-cost application produces excellent results from aerial imagery in a minimum of time with almost no effort needed. Because of its solid and uncomplicated operation, it looks like this application could become an essential part of the aerial archaeologist's toolkit.

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... This method is also known as closed-range photogrammetry, as it was developed at first for proximal sensing ground-based applications, or Structure from Motion (SfM), from one of the algorithms used to reconstruct the 3D scene. In a nutshell, the digital photogrammetric software analyses the photos of an archaeological context or feature, detecting overlapping feature points in the images, and tracking their movement to reconstruct the scene in 3D (Verhoeven, 2011). In our case study, we utilized Agisoft Metashape, a state-of the-art application to produce our 3D taphonomic record. 1 In Group IV, the preservation of each burial typically depends on the elaboration of the funerary container. ...
... In the 2020s, several apps exist for this purpose, with Metashape, 3D Zephyr, and Reali-tyCapture being the most viable and utilized software in archaeological projects. All these apps follow a similar workflow, summarized in Fig. 1 (Verhoeven, 2011). ...
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... Photogrammetry [1,2] is a sophisticated technique used to create accurate 3D models of objects or structures by analyzing and processing multiple 2D images taken from different viewpoints. The core principle behind photogrammetry is triangulation, where common points are identified across two or more images. ...
... By integrating image processing algorithms such as Structure from Motion (SfM), Multi-View Stereo (MVS), Scale-Invariant Feature Transform (SIFT), and Speeded-Up Robust Features (SURF), photogrammetry has achieved greater accuracy and no longer requires specialized cameras for image capture. Through the use of photogrammetry, professionals can create accurate 3D models for analysis, visualization, or preservation, offering a versatile tool that bridges the gap between digital and physical worlds [1,2]. ...
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... The accurate georeferencing of the imagery was performed by the global navigation satellite system (GNSS) positioning of at least 15 ground control points (GCPs) for each flight plan, which were used for image georeferencing during the photogrammetric processing. For more information on the processing procedure and assessment of this method at sites in Haiti, see [38][39][40][41][42][43]. Two drone-based surveys were conducted in 2020 and 2022, respectively. ...
... The accurate georeferencing of the imagery was performed by the global navigation satellite system (GNSS) positioning of at least 15 ground control points (GCPs) for each flight plan, which were used for image georeferencing during the photogrammetric processing. For more information on the processing procedure and assessment of this method at sites in Haiti, see [38][39][40][41][42][43]. ...
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... This method is also known as closed-range photogrammetry, as it was developed at rst for proximal sensing ground-based applications, or Structure from Motion (SfM), from one of the algorithms used to reconstruct the 3D scene. In a nutshell, the digital photogrammetric software analyses the photos of an archaeological context or feature, detecting overlapping feature points in the images, and tracking their movement to reconstruct the scene in 3D (Verhoeven, 2011). In our case study, we utilized Agisoft Metashape, a state-of the-art application to produce our 3D taphonomic record.1 ...
... In the 2020s, several apps exist for this purpose, with Metashape, 3D Zephyr, and RealityCapture being the most viable and utilized software in archaeological projects. All these apps follow a similar work ow, summarized in Fig. 1 (Verhoeven, 2011). ...
Preprint
Full-text available
Mortuary archaeology in the Maya region is complicated by both cultural and natural factors. Distinctive funerary depositional and post-depositional secondary activities, in addition to tropical climate, contribute to the complexity of pre-Hispanic Maya funerary practices. This paper proposes to merge 2D and 3D recording data to obtain a comprehensive understanding of the taphonomic phenomena that affect heavily altered burials at the site of Palenque, Mexico. Employing an archaeothanatological approach, we argue that careful 3D imaging, integrated with earlier produced legacy data, provides additional insight into the formation processes of funerary contexts compared to previous methods. Digital photogrammetric analyses improve our capacity to reconstruct joint articulations of the body and its original funerary deposition in situ. The results of this research elucidate the intentional activities that led to the archaeological arrangement of the grave assemblage. By noticing the degree of articulation and clarifying the pace at which bodies decomposed, these results showcase the depositional sequence of one collective mixed burial from Group IV, a domestic compound in Palenque. These results suggest the viability of 3D methodologies in assessing post-depositional disturbances and movements of the body, both for illuminating funerary taphonomic practices and serving as important recording procedures for the future.
... Thin sections and polished slabs were prepared from the samples; facies were defined in terms of texture, components and paleoenvironmental meaning according to Flügel (2010) and Ćosović et al. (2004; 2018) for specific reference to the Paleogene of the AdCP. Samples' foraminiferal content was photographed with a microscope digital camera using both transmitted and reflected light, whereas we used (mostly but not exclusively) Hottinger (1974), Serra-Kiel et al., (1998), Drobne et al. (2009;2011) and Ibrahimpašić et al. (2015) for taxonomic discriminations and biostratigraphy. ...
... The aerial photographs were processed in Agisoft Metashape software to build the virtual outcrop model of the northern side of the Val Rosandra gully. The well-known workflow of Metashape (Verhoeven, 2011;Tavani et al., 2014;Carrivick et al., 2016) involved the high-accuracy alignment of the photographs followed by an iterative gradual selection filtering and camera optimization steps leading to a final Tie-Point cloud made of ~3M points (Fig. 3a). ...
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... El uso de la metodología SfM (Structure from Motion) para el procesamiento de las imágenes ha sido ampliamente evaluado (Verhoeven, 2011;Kersten et al., 2012;Remondino et al., 2017;Benavides et al., 2020), considerándose hoy en día una herramienta fundamental para la documentación, investigación y difusión del patrimonio arquitectónico y arqueológico. Los datos obtenidos proporcionan una representación completa y objetiva del objeto de estudio, consiguiendo una mayor precisión y detalle que con las encuestas clásicas, aportando datos incluso en aquellos lugares donde no es posible el acceso físico. ...
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... The images were georeferenced, allowing for photogrammetry-based models to be built using Agisoft Metashape Professional software (version 1.7.4). Image alignment was facilitated by Structure-from-Motion algorithms (Ullman, 1979) whereby feature points were used to confirm geolocations (Verhoeven, 2011). The sparse clouds of georeferenced data points were processed using a Multi-View Stereo algorithm to improve the resolution of the model (Scharstein & Szeliski, 2002). ...
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... Η τεχνική αυτή δημιουργεί τριδιάστατα μοντέλα από μια συλλογή φωτογραφιών. Ουσιαστικά, χρησιμοποιείται η τεχνική της παράλλαξης (η διαφορά της σχετικής θέσης ενός αντικειμένου αν αποτυπωθεί από διαφορετικές θέσεις) για την ανακατασκευή ενός πλήρους 3D μοντέλου του Σταθμός βάσης Αυτόνομη πτήση του UAV χώρου ή του αντικειμένου (απόσταση/βάθος) από διδιάστατες εικόνες [13]. Τα βήματα επεξεργασίας των Α/Φ συνοπτικά είναι [14]: ...
Conference Paper
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Unmanned Aerial Vehicles) σε διαδικασίες ψηφιακής απεικόνισης μνημείων. Τα τελευταία χρόνια έχει παρατηρηθεί ραγδαία αύξηση σε εφαρμογές UAVs στη χαρτογράφηση χρήσεων καλύψεων γης από χαμηλό ύψος και την παραγωγή φωτογραμμετρικών προϊόντων υψηλής πιστότητας όπως ορθοφωτοχάρτες και Ψηφιακά Μοντέλα Επιφανείας (Digital Surface Model). Λαμβάνοντας υπόψη την ελαφριά σύνθεσή και το χαμηλό κόστος που τα συνοδεύει, τα UAVs αποτελούν μία ξεχωριστή εναλλακτική εφαρμογή με σκοπό την ταχύτατη ψηφιακή αποτύπωση των πολιτιστικών μνημείων καθώς και τη διαχρονική παρακολούθηση της κατάστασής τους. Λέξεις κλειδιά: Πολιτιστική κληρονομιά, ψηφιακή απεικόνιση, UAV. 1. ΕΙΣΑΓΩΓΗ Τα πολιτιστικά τοπία γενικότερα και τα μνημεία ειδικότερα αποτελούν ταυτόχρονα αντικείμενα μέσα από τα οποία υφίσταται η δυνατότητα ανίχνευσης ιστορικών και κοινωνικών θεμάτων στο παρελθόν αλλά και χώρων που αντανακλούν πεδία δράσης άλλοτε επιβεβαιώνοντας και άλλοτε αναιρώντας σύγχρονα ζητήματα όσον αφορά στον πολιτισμό και την κοινωνία. Ανεξάρτητα από το πόσο γραφικά μπορεί να είναι, τα πολιτιστικά τοπία είναι τόποι με πολιτικές, πολιτιστικές και κοινωνικές επιδράσεις στη σύγχρονη ζωή [1]. Η διατήρηση της υλικής πολιτιστικής κληρονομιάς, ως ερευνητικό πεδίο εμπλέκει και απαιτεί τη συνεργασία διαφόρων επιστημονικών διακριτών πεδίων. Επιστήμονες, όπως για παράδειγμα Αρχαιολόγοι, Ιστορικοί, Λαογράφοι, Μουσειολόγοι, Κοινωνικοί Ανθρωπολόγοι, Συντηρητές Έργων και Μνημείων οφείλουν να συνεργαστούν με συναδέλφους Χημικούς, Φυσικούς, Γεωλόγους, Βιολόγους, Περιβαλλοντολόγους, Μηχανικούς, Αρχιτέκτονες, Μεταλλειολόγους [2]. Αποτελεί γεγονός αναντίρρητο ότι μία από τις βασικές πνευματικές και ψυχικές ανάγκες κάθε κοινωνίας είναι η συνειδητοποίηση και η γνώση του παρελθόντος της που διασφαλίζει την ομαλή λειτουργίας της. Η άγνοια του προκαλεί προβλήματα αντίστοιχα με τα προβλήματα που δημιουργεί η έλλειψη μνήμης στην ομαλή, πνευματική και ψυχική λειτουργία ενός ατόμου. Η μνήμη μίας κοινωνίας ή σε μεγαλύτερη κλίμακα ενός λαού είναι το σύνολο των υλικών και πνευματικών έργων που δημιούργησε ο λαός αυτός στο χώρο και στο χρόνο κατά το παρελθόν. Αν οι αποδείξεις αυτών των πράξεων-που στη συγκεκριμένη περίπτωση είναι τα μνημεία-λείψουν και δημιουργηθεί κενό στην ιστορική συνέχεια ενός λαού ή μίας κοινωνίας, τότε η ζωή η ίδια θα αναγκαστεί να βάλει στη θέση τους υποκατάστατα, γεγονός που περιθωριοποιεί την αυθεντικότητα [3]. Αυτό που διαφοροποιεί τη σύγχρονη προσέγγιση για την κληρονομιά είναι η συνείδηση της ιστορικότητας η οποία ήταν απούσα τους προηγούμενους αιώνες. Αυτή η απουσία της συνείδησης είναι ο λόγος για τον οποίο, διαμέσου των αιώνων, πολλά σημαντικά μνημεία καταστράφηκαν ή μετασχηματίστηκαν. Τα μνημεία ωστόσο, δεν χαρακτηρίζονται από την υλική τους υπόσταση μόνο. Δεν είναι παρά μία κληρονομιά που κρύβει μέσα της αιώνες ή και χιλιετίες γνώσης και αυτή η γνώση επιβάλλεται να διατηρηθεί και να υπάρχει μέσω των επόμενων γενεών. Αυτά τα απτά και ιστορικά τεκμήρια, τα μνημεία, αντανακλούν στην πραγματικότητα τον τρόπο ζωής και αισθητικής αρκετά παλιότερων εποχών. Ταυτόχρονα λοιπόν με την υλική τους υπόσταση, τα μνημεία είναι φορείς άυλων στοιχείων, των οποίων η εγκυκλοπαιδική γνώση και πολύ περισσότερο η κατανόηση τους συνάδει με την προστασία και την καταγραφή τους. Αρωγός σε αυτήν την κατεύθυνση είναι η τεχνολογία και τα επιτεύγματα της μέσω της ψηφιακής απεικόνισης των μνημείων χρησιμοποιώντας τα κατάλληλα εργαλεία, ένα εκ των οποίων είναι και τα επονομαζόμενα UAV (Unmanned Aerial Vehicles). Ο αγγλικός όρος UAV ανταποκρίνεται στον όρο Μη Επανδρωμένο Αεροναυτικό Όχημα, που αποτελεί ένα αεροσκάφος, σχεδιασμένο να λειτουργεί χωρίς την παρουσία του ανθρώπου σε αυτό [4]. Παράλληλα το UAV αποτελεί ένα από τα υποσυστήματα της γενικότερης έννοιας Μη Επανδρωμένο Αεροναυτικό Σύστημα (Unmanned Aerial System-UAS). Το UAS περιλαμβάνει το UAV, το σταθμό βάσης και τα συστήματα επικοινωνίας [5].
... The UAV image processing was conducted using Agisoft Metashape 2.0.1. This software is renowned for its reliability and widespread adoption in the field of 3D reconstructions from digital imagery [100]. The processing workflow of each set of images was performed independently in Metashape, where the alignment process was configured to high accuracy and no point limit settings. ...
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In recent decades, the scientific community has increasingly focused on extreme events linked to climate change, which are leading to more intense and frequent natural disasters. The Mediterranean can be considered a hotspot where the effects of these changes are expected to be more intense compared to other regions of the planet. Italy is not exempt; in fact, with its extensive shoreline, it is particularly vulnerable, especially to high sea levels and coastal erosions. In this framework, from late October to early November 2023, six storm surges occurred in the Gulf of Trieste (NE Italy). These events, characterized by winds from 190°N to 220°N and the significant wave height, which reached up to 1.81 m nearshore—an uncommon meteorological condition in the northern Adriatic Sea—caused the occurrence of eight coastal sinkholes and substantial damages to man-made structures. Thanks to Unmanned Aerial Vehicles (UAVs) and their derived products (high-resolution orthomosaics, Digital Elevation Models—DEMs, and point clouds), it was possible to study these features over time, enabling long-term coastal dynamics monitoring, which can be crucial for timely and effective response and restoration efforts.
... Metashape has been popular among archaeologists for over a decade now, most likely due to its facile graphical interface and good general results (e.g. Verhoeven 2011;Forte et al. 2012;Olson et al. 2013;Brandolini et al. 2020). Metashape also supports automatic self-calibration, which was also used in our project to streamline the workflow. ...
Article
Photogrammetric techniques have become commonplace in archaeology during the last two decades. During recent decades, the development of digital photography and the introduction of highly automated software with intuitive user interfaces has made 3D photogrammetry easily accessible for even the less-technologically adept fieldworkers. Archaeologists without special training in the technologies and theories behind photogrammetry can now produce accurate and visually impressive three-dimensional models of their research subjects. This article describes the measurement and documentation methodology used in an archaeological excavation project conducted in Photike, Greece, in 2021 by a Finnish-Greek cooperation. Photogrammetric modelling has been used in coordination with total stations in various contexts: in addition to documenting the uncovered architectural structures and remains, the method has also been applied to reproduce different stratigraphical phases of the excavation process, among other applications.
... For the photogrammetry processing of the 656 captured pictures, we used Agisoft Metashape, commonly used thanks to the high quality of the resulting output models (Benassi et al., 2017;Burns and Delparte, 2017;Cook, 2017). The processing was articulated in a few key steps (workflow), described in detail by Verhoeven (2011), Brunier et al. (2016 and Tibaldi et al. (2020b), which led to the creation of the DSM, the orthomosaic and the 3D Tiled model as final products ( Fig. 5A-B). The adopted workflow is presented in detail in Bonali et al. (2019); the photogrammetry processing settings and results are reported in Tables 1 and 2. ...
... Additionally, to create a comprehensive view of the accident site, overlapping images can be merged using image feature points [21]. Verhoeven et al. [22] utilized the Structure from Motion (SfM) algorithm to create a sparse point cloud from overlapping photographs containing sequential information. Liu et al. [23] implemented the UAV photographic modeling method in traffic accident surveys. ...
Article
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Current road accident survey methodologies often overlook the low-brightness and occlusion conditions, and this study specifically fuses UAV-borne and terrestrial LiDAR data, to facilitate rapid and high-precision accident scene monitoring for these scenarios. Firstly, UAV-borne LiDAR is utilized to acquire point cloud data from the perspective of wide-view. Meanwhile, both the side overlap rate and flight altitude of UAV mapping are considered, and the impacts of them on the accident scene modeling accuracy are explored in low-brightness scenario. Then, the terrestrial LiDAR scanning is adopted to model the accident scene under occlusion condition. Secondly, the Gaussian filtering and voxelization downsampling are conducted to improve the quality of point cloud data and the modeling speed. Thirdly, for enhancing the feature fusion, the Normal Distributions Transform (NDT) algorithm is adopted to register the UAV-borne and terrestrial LiDAR data. Finally, the DJI M300RTK UAV is selected, and two traffic accident scenes of low-brightness and occlusion conditions are conducted. A 50% side overlap rate and a 15m altitude of UAV mapping are recommended, to construct an efficient and accurate accident scene investigation. In addition, compared with the manual taping, the total station measurement and photography method, the monitoring accuracy of the proposed method is optimal with an RMSE of 0.0491. This shows that it is promising to adopt the proposed method to investigate the low-brightness and occlusion traffic accident scenes. Moreover, the limitations and future research directions of the proposed method are presented.
... The accurate georeferencing of the imagery was performed by the GNSS (Global Navigation Satellite System) positioning of at least 15 GCPs (Ground Control Points) for each flight plan, used for image georeferencing during photogrammetric processing. For more information on the processing procedure and assessment of this method at sites in Haiti, see [11][12][13][14][15][16]. Two drone-based surveys were conducted in 2020 and 2022, respectively. ...
Preprint
Full-text available
Evaluating flood risk though numerical simulations in areas where hydrometric and bathymetric data are scarcely available is a challenge. This is however of paramount importance, particularly in urban areas, where huge losses of human life and extensive damage can occur. This paper focuses on the June 2-3, 2023 event at Léogâne in Haiti, where the Rouyonne River partly flooded the city. Water depths in the river were recorded since April 2022 and a few discharges were measured manually but it was not sufficient to produce a reliable rating curve. Using a uniform flow assumption combined with the BaRatin method (Bayesian rating curve), it was possible to extrapolate the existing data to higher discharges. From there, a rainfall-runoff relation was developed for the site using the AtHyS distributed hydrological model, which allowed to determine the discharge of the June 2023 event, which was estimated as twice the maximum conveying capacity of the river in the measurement section. Bathymetric data were obtained using drone-based photogrammetry and two-dimensional simulations were carried out using the WATLAB computational environment to represent the flooded area and the associated water depths. By comparing the water depths of 21 measured high-water marks with the simulation results, we obtain KGE and NSE criteria of, respectively, 0.890 and 0.882. This allows us to conclude that the model is sufficiently accurate and could be used by flood managers and decision-makers to assess flood risk and vulnerability in Haiti.
... Structure from Motion (SfM) photogrammetry is now widely used to provide detailed 3-D description of various natural and anthropogenic objects of interest or systems (see for example reviews from Carrivick et al. 2016;Eltner et al. 2016. Moreover, Structure from Motion has allowed for extracting new insights from archival aerial imagery (e.g., Verhoeven 2011;Salach 2017;Sevara et al. 2017) and hence have access to an unprecedented historical depth for the monitoring of 3-D change. Still, in order to compare data acquired at different epochs, one must ensure that multi-temporal data share a common geometric reference. ...
Chapter
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This chapter aims to check the potential of the Time-SIFT method on varied test cases with different spatiotemporal scales, from the millimeter/minute to the kilometer/decade. It proposes five test cases to demonstrate the ability of the Time-SIFT method to provide coherent multi-temporal 3-D and/or 2-D datasets with limited or no external registration data. To demonstrate the ability of the Time-SIFT method to produce coherent multi-temporal dataset in various situations, the chapter presents distinct case studies: (i) spatiotemporal scales of the image datasets (ii) relative magnitude and spatial patterns of the expected changes; (iii) different data sources; and (iv) varied target phenomena. The authors expect that the Time-SIFT method will help to unlock the existing multi-temporal stereoscopic image archive for a broad range of change detection studies. Finally, to support access to the Time-SIFT method, the authors have opened it up as a module to the Agisoft Metashape software.
... There is no universal rule for how many shots should be taken or how much overlap should apply between images because every scenario is unique. However, it is recommended to use at least three images per crucial point and take as many photos as possible [10], [12]. The processing time, however, will grow proportionally with the amount of captured photos and photographs. ...
Article
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In recent years, the extensive need for high-quality acquisition platforms for various 3D mapping applications has rapidly increased, especially in sensor performance, portability, and low cost. Image-based UAV sensors have overwhelming merits over alternative solutions for their high timeline and resilience data acquisition systems and the high-resolution spatial data they can provide through extensive Computer Vision (CV) data processing approaches. However, applying this technique, including the appropriate selection of flight mission and image acquisition parameters, ground settings and targeting, and Structure from Motion-Multi-View Stereo (SfM-MVS) post-processing, must be optimized to the type of study site and feature characteristics. This research focuses on optimizing the application of UAV-SfM photogrammetry in an urban area on the east bank of the Tigris River in the north region of Iraq following optimized data capturing plan and SfM-MVS photogrammetric workflow. The research presented the practical application of optimized flight planning, data acquisition, image processing, accuracy analysis, and evaluation based on ground truth targets designed for the proposed optimal routine. This includes investigating the influence of the number and distribution of GCPs, flying heights, and processing parameters on the quality of the produced 3D data. The research showed the potential of low-budget and affordable UAV devices to deliver robust 3D products in a relatively short period by demonstrating the value of UAV-based image techniques when contributed to CV algorithms. The results showed powerful outcomes with validation errors reaching a centimeter-level from 100 m flying height when applying the optimized flight plan settings and the appropriate selection of the number and distribution of GCPs. The study established a streamlined UAV mapping procedure, demonstrated the viability of UAV use for 3D mapping applications, offered suggestions for enhancing future applications, and offered clues as to whether or not UAVs could serve as a viable alternative to conventional ground-based surveying techniques in accurate applications.
... For georeferencing of the point clouds, the surveyed GCPs were identified and marked on as many images as possible in Agisoft Metashape. All sparse point clouds from UAV and USV surveys were then transformed into dense point clouds by an MVS algorithm, operating directly on pixel scale and hence enabling highly detailed 3D reconstructions (Verhoeven, 2011). ...
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Uncrewed aerial vehicles (UAVs) are frequently used in glaciological applications, among other things, for photogrammetric assessments of calving dynamics at glacier termini. However, UAVs are often limited by battery endurance and weight constraints on the scientific payload that can be added. At Sálajiegna, the largest freshwater calving glacier in Sweden, we explored the combined use of a versatile maritime robot (uncrewed surface vehicle, USV) and a UAV to characterise Sálajiegna's short-term and seasonal calving front dynamics and mass loss. For this, a photogrammetric payload suite was integrated into the USV. Consecutive USV surveys of Sálajiegna's front, followed by point cloud based calving detection and surface-reconstruction based volume quantification, allowed for a detailed description of calving-induced terminus changes and is hence suggested as a viable alternative to the differencing of digital elevation models. By combining USV and UAV measurements, we identify sectors of high and low calving activity, a calving front retreat of up to 56 m and a thinning rate in the terminus region of 5.4 cm d ⁻¹ during the summer of 2022.
... Las comparaciones entre softwares disponibles comercialmente, han señalado que Agisoft Metashape proporciona mayores tasas de alineación de imágenes, una resolución ortomosaica más fina y distancias de muestreo de suelo mejoradas (Fraser y Congalton, 2018;Przybilla et al., 2019), destacándolo como un paquete de software particularmente común utilizado para la producción de conjuntos de datos 3D a través de IBM (Hill et al., 2014;Jones y Church, 2020;Magnani et al., 2020;Verhoeven, 2011). ...
... The photogrammetric processing was completed using Agisoft Metashape Structure-from-Motion (SfM) and Multi-View-Stereo (MVS) algorithms (Verhoeven, 2011), which first performed an automatic image alignment. Upon identifying the GCPs in the images the dataset becomes rigorously georeferenced, with a total root mean square error (horizontal and vertical) of 3 cm. ...
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This paper discusses the archaeological research and historical contextualisation of the Alto da Raia enclosure located on the border between northern Portugal and Galicia, identified as a possible Roman camp, following an interdisciplinary and multi-proxy approach. This included archaeological excavation, remote sensing and geophysical survey, as well as sample collection for archaeobotanical and geochemical studies by means of chemical and mineralogical analyses and absolute dating using radiocarbon and luminescence protocols. The results seem to indicate that this site was a Roman camp probably built and occupied between the 1st century BC and the 1st century AD, when major changes occurred in Northwest Iberia driven by the expansion of the Roman State. The camp overlaps with previous prehistoric occupations possibly dating back to the Bronze Age and Iron Age.
... The use of GCPs is needed to scale the 3D point cloud using the BBA. A description of the SfM procedure in Metashape ® along with commonly used parameters can be found in (Cutugno, Robustelli, and Pugliano 2022b;Doneus et al. 2011;Verhoeven 2011). ...
Article
Assessing breakwater damage following intense storm events is crucial for preventing failures that can compromise safety and service quality. This study focuses on assessing the impact of a severe storm event that took place in November 2022, resulting in significant damage to the Amalfi breakwater in Campania, Italy. The breakwater damage and repair armor unit volumes have been evaluated with an integrated approach consisting of a combination of Differential Global Navigation Satellite System (DGNSS) surveys and Unmanned Aerial Vehicle (UAV) photogrammetry. The assessment of the added areas gained for the breakwater reconstruction has been performed using the UAV. The final goal was to estimate a damage parameter to give an assessment of the breakwater stability and to find a rapid and cost-effective method to evaluate the necessary rehabilitation works. The method, being relatively rapid, can also be applicable in the immediate aftermath of a storm surge or even as a systematic monitoring of the breakwater conditions. The findings of the study highlight the importance of monitoring coastal structures to prevent failure mechanisms from occurring in response to future, increasingly frequent and intense storm events.
... Based on these data DSM and RGB orthophoto mosaics of the settlement mounds and their surroundings were created. Feature points between overlapping 2D images were correlated to calculate the position and orientation of the camera during the image acquisitions and to triangulate the 3D position of feature points itself (Plets et al., 2012;Verhoeven, 2011). To mitigate possible vertical offset, a correlation with the D-GPS-referenced Ground Control Points was obtained. ...
Article
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Along the lower course of the Rioni and several minor rivers, more than 70 settlement mounds (local name: Dikhagudzuba ) have been identified by field surveys and remote sensing techniques. They give evidence of a formerly densely populated landscape in the coastal lowlands on the Colchian plain (western Georgia) and have been dated to the Bronze Age. As yet, limited information is available on their internal architecture, the chronology of the different layers and their palaeoenvironmental context. Based on archaeological sources, remote sensing measurements of three mounds and sediment cores from one mound and its closer surroundings, our study presents a review of the relevant literature and reveals the internal structure, distribution and spatial extent of the mounds. Geochemical and sedimentological analyses of element contents (X‐ray fluorescence) and granulometry helped to identify different stratigraphical layers and differentiate between natural facies and anthropogenic deposits; using the Structure‐from‐Motion technique the mounds' dimensions were calculated. The studied settlement mounds had relatively small dimension (varying from 30 to 100 m in diameter) and were similar in their stratigraphy. Measurement of elements that can identify types of human activity, notably metals and phosphorus, suggest changing intensities of human occupation, pastoral agriculture and metalworking through the occupation sequence. According to the ¹⁴ C chronology, the formation of the settlements occurred during the first half of the second millennium B.C., which confirms the archaeological interpretation of their Bronze Age origin. The narrow age difference between the lowermost and uppermost anthropogenic layers indicates an intentional construction of the mounds, rather than a successive accumulation of construction debris due to the disintegration of loam bricks by weathering. Therefore, they are indeed mounds and not tells . It is most likely that the characteristic circular moats that surround them were the source of their construction material. Fluvial and alluvial processes in a warm and humid climate dominated the environment of the mounds.
... Agisoft Metashape software was used to process the UAV images. This software is robust and widely used in the 3D reconstruction of digital images (Verhoeven 2011). ...
Article
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The inventory and categorization of an extensive coastal boulder assemblage originating from storm wave transport on the coastline of Fenoliga Island (Northern Adriatic Sea, southern Istria, Croatia) are presented and discussed herein. The study adopted the use of a commercial Uncrewed Aerial Vehicle (UAV) and Structure from Motion-MultiView Stereo (SfM-MVS) photogrammetry for the construction of a 3D model of the island. A Digital Elevation Model (DEM) and an orthomosaic were produced and employed for the mapping of the boulder assemblage in a GIS. In total, 592 boulders were identified and mapped. Using SfM-MVS-derived products allowed for the identified boulders to be categorized based on size classification. Amassed data relating to the boulder characteristics was inserted and stored in a GIS, including the results of a comparative assessment with historical Google Earth imagery which enabled the ‘quantification of boulder transport over a 9-year timeframe’. Field evidence indicates that boulders were created in-situ via the quarrying of bedrock strata by breaking waves causing increased water pressure within preexisting surfaces of weakness such as bedding planes and sub-vertical fractures. Once detached, the boulders were transported and deposited during storm wave events. Repeated storm events can further displace previously detached clasts.
... After creating the dense point cloud, we can construct the proper 3D model by applying triangulation algorithms to build a mesh. Additionally, with the exterior and interior orientation parameters, we can | 461 | GEODETSKI VESTNIK | 67/4 | RECENZIRANI ČLANKI | PEER-REVIEWED ARTICLES produce orthophotos, where all objects with a certain height are accurately positioned in a 2D plane (Verhoeven, 2011). ...
Article
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In recent years, unmanned aerial vehicles (UAVs) have become increasingly important as a tool for quickly collecting high-resolution (spatial and spectral) imagery of the Earth's surface. The final products are highly dependent on the choice of values for various parameters in flight planning, the type of sensors, and the processing of the data. In this paper ground control points (GCPs) were first measured using the Global Navigation Satellite System (GNSS) Real-Time Kinematic (RTK) method, and then due to the low height accuracy of the GNSS RTK method all points were measured using a detailed leveling method. This study aims to provide a basic assessment of quality, including four main aspects: (1) the difference between an RGB sensor and a five-band multispectral sensor on accuracy and the amount of data, (2) the impact of the number of GCPs on the accuracy of the final products, (3) the impact of different altitudes and cross flight strips, and (4) the accuracy analysis of multi-altitude models. The results suggest that the type of sensor, flight configuration, and GCP setup strongly affect the quality and quantity of the final product data while creating a multialtitude model does not result in the expected quality of data. With its unique combination of sensors and parameters, the results and recommendations presented in this paper can assist professionals and researchers in their future work.
... 9 e 3D models of these nds have been imported in the geodatabase together with the other data in order to be visualised and analysed in the virtual environment (Figure 9). For what concerns the 9 e 3D models were generated respectively through a NextEngine laser scanner and through the PhotoScan Agiso so ware (Verhoeven 2011). e use of the two techniques was done at the beginning for the integration of the two kind of models for a major accuracy. ...
... To generate the orthomosaic reflectance maps, the Agisoft Metashape (Agisoft LLC) was used. The software is based on a structure from a motion algorithm (Verhoeven, 2011). To complete the third and fourth main steps, the orthomosaic reflectance map was imported into R statistical software (ver. ...
Article
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Precision agriculture (PA) is an agronomic management that allows the parsimonious use of agronomic inputs according to the crop's actual spatiotemporal needs. The most important agronomic practice of PA is the site‐specific management (SSM) of agronomic inputs. To apply SSM, the number and location of homogeneous zones must be defined. Nowadays, many approaches are used to define the number of zones in an arbitrary and constant way, such as high‐, medium‐, and low‐input zones, without a priori statistical analysis. Two combined field experiments were carried out on durum wheat (Triticum turgidum subsp. durum Desf.) in central Italy to agronomically validate an automatic approach aimed at defining the number and position of the homogeneous zones using multispectral images. For both sites, at stem elongation and anthesis, the dry biomass per square meter and Soil Plant Analysis Development (SPAD) readings were measured, while at crop maturity the yield was measured. This approach uses multispectral images as source data and uses the gap statistic index to determine the correct number of zones. The management zones created were well‐fitted with the experimental design of both sites, and the validation was made by the statistical analysis performed on yield data, SPAD, dry biomass, and normalized difference red edge index with an average difference of 40.2%, 28.5%, 57.5%, and 37.4%, respectively, between the management zones. The approach could be scaled by using the multitemporal multispectral images provided by satellite constellation, which enables farms and societies to take advantage of all the economic and environmental benefits of PA.
... Consequently, it is of paramount importance to obtain an accurate 3D overview of the site and its surroundings (Verhoeven 2011;Verhoeven et al. 2012), in order to create a 3D scientific visualisation environment in which old plans are integrated into new ones. Such an environment enables the investigation of the site from various view points and from different altitudes; changing viewing conditions, such as light, shading and colours may reveal hidden architectural features or patterns in their spatial distribution not observable otherwise. ...
... Os algoritmos SfM são conhecidos por sua capacidade de reconstruir uma nuvem de pontos esparsos de cenas que foram fotografadas por uma série de fotografias superpostas. Quando complementados por algoritmos de correspondência estéreo, modelos tridimensionais detalhados podem ser construídos a partir dessas coleções de fotografias de uma maneira totalmente automatizada (VERHOEVEN, 2011). ...
Thesis
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Com o advento de novas tecnologias e a capacidade de aquisição de imagens de muito alta e altíssima resolução espacial, em inglês, respectivamente, Very High Resolution (VHR) e Ultra-High Resolution (UHR), por meio de sensores imageadores embarcados em Aeronaves Remotamente Pilotadas (ARP) ou satélites, o uso do Sensoriamento Remoto (SR) é cada vez mais ampliado. Contudo, a classificação de áreas urbanas continua sendo um desafio, devido a quantidade e variabilidade de materiais existentes no ambiente urbano. Nesse sentido, a abordagem GEOBIA (Geographic Object-Based Image Analysis) tem ganhado significativo espaço no SR. A classificação orientada a objeto vem obtendo melhores resultados que a abordagem pixel-a-pixel, pois caracteriza melhor os alvos da imagem, principalmente em ambientes urbanos. Neste trabalho, foram utilizadas imagens de diferentes resoluções, obtidas com ARP, e imagens satelitais de alta resolução. O desafio proposto foi separar 21 diferentes classes de uso e cobertura do solo do ambiente urbano, utilizando imagens UHR e VHR, com apenas três bandas espectrais da região do visível (RGB). A segmentação foi realizada em duas etapas: Segmentação Multiresolução, seguida pela Segmentação por Diferença Espectral. Foram realizados diversos testes de segmentação, variando-se os parâmetros relacionados (escala, forma, compacidade e diferença espectral), com o objetivo de encontrar uma segmentação adequada. Considerou-se o uso de 8 classificadores supervisionados, utilizando-os individualmente (Random Forest (RF), Árvore de Decisão, Multilayer Perceptron (MLP), Support Vector Machine (SVM), AdaBoost, Deep Learning (DL) e Logistic Models Tree (LMT)) e em conjunto (Vote ou Ensemble). Foram realizadas 184 classificações distintas, divididas em 4 estudos de caso considerados. Para a validação dos resultados, foi gerada uma Verdade de Campo, contendo os valores de referência para os segmentos da imagem. Para cada classificação realizada, foi gerada uma Matriz de Confusão, comparando o valor de referência com o valor obtido, a partir da qual realizou-se a análise do valor da acurácia alcançada, por meio da Exatidão Global (EG) e Índice Kappa (IK). Também foram registrados os valores do Tempo Total de Processamento (TTP). Na literatura, as métricas avaliativas baseiam-se na acurácia e no TTP. Porém, uma relação entre os dois fatores não é considerada. Propôs-se a criação de um Índice Relacional de Exatidão e Tempo de Processamento (APTRI) para avaliar os classificadores no que tange à relação EG-TTP. Os resultados foram analisados considerando-se três diferentes situações nas quais as prioridades são a EG, o APTRI ou o TTP, compilando os valores com relação à resolução, classificador e aplicação. Os melhores resultados foram obtidos: em relação ao TTP, pelo classificador Árvore de Decisão; em relação à EG, pelos classificadores RF, AdaBoost e Vote; e em relação EG-TTP, obtido por meio do cálculo do APTRI, os classificadores: RF, AdaBoost, MLP e DL.
... The application of aerial photography is far-reaching. It includes the fields of geology (Ray 1960), forestry (Spurr 1948), archaeology and building reconstruction (Reeves 1936, Verhoeven 2011, phytopathology (Brenchley 1968), ecology (Morgan et al. 2010) and many others. Pioneering work was done by Bernhard and Michael Grzimek who established aerial census methods, including aerial photography, to estimate population sizes of dominant characteristic animal species of the Serengeti-Mara ecosystem (Grzimek & Grzimek 1960). ...
Research
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This discussion paper explores the multiple roles of photography in the realms of science and education, celebrating its diverse applications, while offering a cautious perspective on its use. The authors advocate that photography is a useful tool for sustainability transfer underscoring the ways in which photography can transcends barriers in education and research communication. The paper begins by highlighting the value of photography in education and research, providing examples of its use. Light is shed on the utility of photography in report writing and scientific publications, and cautionary notes are provided on some of the limitations of photography in research. Finally, personal reflections and lessons learned along the authors own photographic journeys are shared before some closing remarks are provided. The authors do not aim to give a systematic, near comprehensive or technical overview of the various aspects of photography, instead, they provide impulses and share experiences when it comes to the application of photog-raphy in teaching and research. As a fitting tribute to the subject matter, the paper is authored by two scientists who are also passionate photographers. With this paper the authors hope to pro-mote the responsible and ethical use of photography and to inspire others to see its value in enhancing knowledge and sustainability transfer.
... With regard to crop height monitoring, Zarco-Tejada et al. [24] and Luo et al. [25] obtained high-resolution images through visible light (RGB) digital cameras and LIDAR, attached to fixed-wing aircraft, and used them to estimate the height of olive trees and the plant height of low wetland vegetation, respectively. Verhoeven [26] and Weiss and Baret [27] acquired high-resolution images through visible light cameras mounted on UAVs, constructed a DSM for crops using dynamic structural algorithms and a 3D reconstruction method, and calculated plant height of crops and vines. The aforementioned studies all reflected the advantages of UAVs, such as carrying convenience, high flexibility, and short operating cycles [27,28]. ...
Article
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The application of unmanned aerial vehicle (UAV) remote sensing technology for high-throughput acquisition of phenotypic values of field plant height is of great significance in plant height monitoring of wheat varieties (lines). Based on the UAV, mounted with high-resolution digital cameras, a low-altitude remote sensing platform was built to obtain images of the Berkut/Worrakatta recombinant inbred lines (RIL) wheat population (297 lines). The optimal digital surface model (DSM) for plant height extraction was constructed by combining the actual wheat plant heights measured in the field. Using a wheat 50K SNP chip, quantitative trait locus (QTL) analysis was performed for field plant height of the RIL population using UAV plant height data to detect the locus related to plant height. We verified the effectiveness of QTL analysis using the UAV plant height data. The results of the DSM plant height extraction method showed that the plant height extraction models during the entire growth period had a highly significant correlation (p < 0.001); the measured plant height correlated with the predicted plant height, with prediction model accuracy R2 = 0.7527 and verification model accuracy R2 = 0.8214. QTL analysis was conducted on the manually and UAV-measured plant height traits. For the manually measured plant height phenotypes, one locus related to plant height was detected on wheat chromosome 6A and explained 13.12% of phenotypic variation. For the UAV-measured phenotypes, one locus related to plant height was also detected on wheat chromosome 6A and explained 9.62% of phenotypic variation. The QPH.xjau-6A locus on chromosome 6A, which featured in the results of the two measurement methods, is a stable locus, indicating that the mapping results obtained using the actual plant height values were in good agreement with those obtained using the UAV extracted values. Three candidate genes related to plant height were screened: they encode protein kinase, NAC domain protein, and cytochrome P450, respectively. Therefore, this study provided reference information for monitoring plant phenotype and growth of wheat and also for the extraction of plant height for wheat breeding in the future.
... The images collected during the drone surveys with the RGB camera were processed into orthophotos and grid-based DSMs of the glacier and its surroundings using a structure-from-motion (SfM) workflow [54,55] in Agisoft Metashape v. 1.7.2 (Agisoft LLC, St. Petersburg, Russia). A detailed description of the SfM algorithms used in Metashape can be found in Verhoeven [56]. ...
Article
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Glacier surfaces are highly heterogeneous mixtures of ice, snow, light-absorbing impurities and debris material. The spatial and temporal variability of these components affects ice surface characteristics and strongly influences glacier energy and mass balance. Remote sensing offers a unique opportunity to characterize glacier optical and thermal properties, enabling a better understanding of different processes occurring at the glacial surface. In this study, we evaluate the potential of optical and thermal data collected from field and drone platforms to map the abundances of predominant glacier surfaces (i.e., snow, clean ice, melting ice, dark ice, cryoconite, dusty snow and debris cover) on the Zebrù glacier in the Italian Alps. The drone surveys were conducted on the ablation zone of the glacier on 29 and 30 July 2020, corresponding to the middle of the ablation season. We identified very high heterogeneity of surface types dominated by melting ice (30% of the investigated area), dark ice (24%), clean ice (19%) and debris cover (17%). The surface temperature of debris cover was inversely related to debris-cover thickness. This relation is influenced by the petrology of debris cover, suggesting the importance of lithology when considering the role of debris over glaciers. Multispectral and thermal drone surveys can thus provide accurate high-resolution maps of different snow and ice types and their temperature, which are critical elements to better understand the glacier’s energy budget and melt rates.
... Agisoft Metashape (Agisoft LLC) was used to generate the orthomosaic reflectance map. The software was 240 based on the structure-from-motion (SfM) algorithm (Verhoeven, 2011 ...
... In archaeological research, image-based 3D reconstructions in the form of SfM models have become regularly integrated in various forms to document and visualize cultural heritage (e.g. De Reu et al., 2014;De Reu et al., 2013;Green et al., 2014;Verhoeven 2011;Verhoeven et al., 2012). The wide adoption of photogrammetry is mainly due to it being relatively inexpensive, with no need of special set ups, and easy to use (Strasser et al., 2018). ...
Article
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The last decade has seen a steady increase in the application of virtual 3D approaches in cultural heritage research. Although a large literature exists about the advantages of 3D methods in this field, here we go one step further and elucidate a) how image-based 3D reconstructions can be displayed in virtual reality (VR) space using freeware game engine software and low-cost VR hardware and b) highlight the relative benefits and advantages with a focus on interactive museum displays of relatively large archaeological objects. Specifically, we present three 3D models of different stone grave structures from the Neolithic necropolis of Lenzburg (Northern Switzerland, 4450-3500 BCE). The site has been excavated in 1959/60 and certain graves were subsequently preserved for museum display. By means of VR applications, it is now possible to experience these approximately 6000-year-old tombs with an innovative approach circumventing various barriers or constraints and offering interactive display options.
... A utilização de pontos de controle (Ground Control Points -GCPs) permite a geração de modelos georreferenciados como o Digital Surface Model (DSM), ou seja, um modelo topográfico com todas as estruturas como vegetação e construções. O DSM combinado com as posições da câmera e os parâmetros de orientação interior permitem a geração do ortomosaico/ortofoto, onde os objetos podem ser posicionados com precisão FU-RUKAWA;HERNÁNDEZ, 2015;VERHOEVEN, 2011). ...
... Data processing of images was performed with Agisoft Metashape software (LLC. St. Petersburg, Russia) [60] using the structure from motion (SfM) technique [61,62]. Considering the large size of the data set, the 3D model was processed by dividing it into France)). ...
Article
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Three-dimensional modeling and non-invasive diagnosis are fundamental prerequisites for planning reliable assessments of the seismic vulnerability, renovation and conservation of heritage buildings. In the case of multi-layered, huge and complex ancient constructions, various problems can be encountered in the early design phases of interventions, among which there is often a lack of an adequate building documentation. Such issues include drawings that are without a metric scale, not detailed, not updated or not reflecting the real situation. In addition, the fragility of these constructions requires an accurate census of every sign of deterioration in order to prepare an ad hoc intervention for the site. As an example, in this paper, the results of a survey regarding the Patriarchal Basilica of Santa Maria Assunta (Aquileia, Italy) are reported. The basilica has a rich history of about two thousand years. in which each era has marked the actual architectural layout with its own culture and art. The result is an intricate association of complementary and/or interdependent elements that make the building very complex. Given the need to obtain accurate documentation, a realistic representation and a simulation of the criticalities of the structure, which previously did not exist or were not sufficiently accurate, a multi-methodological and multi-scale diagnosis was performed. In detail, the ground-penetrating radar (GPR) technique was applied to verify the presence of structures still buried under some internal surfaces, and a topographic survey, terrestrial laser scanning (TLS), and structure for motion (SfM) aerial and terrestrial photogrammetry were integrated for the detailed survey of the entire internal and external macro-structure. The resulting outcome provided the comprehensive information needed for preparing projects for the preservation, management and restoration of the basilica and the buildings connected to it.
... All data were processed using the SfM workflow as implemented in Agisoft Photoscan Pro V1.4. This commercial software has been widely used within the academic community, and numerous resources discuss its workflow in more detail (Verhoeven, 2011;Wigmore andMark, 2017, 2018;Agisoft, 2016). The core workflow used for this study is summarised below. ...
Article
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Alpine ecosystems are experiencing rapid change as a result of warming temperatures and changes in the quantity, timing and phase of precipitation. This in turn impacts patterns and processes of ecohydrologic connectivity, vegetation productivity and water provision to downstream regions. The fine-scale heterogeneous nature of these environments makes them challenging areas to measure with traditional instrumentation and spatiotemporally coarse satellite imagery. This paper describes the data collection, processing, accuracy assessment and availability of a series of approximately weekly-interval uncrewed-aerial-system (UAS) surveys flown over the Niwot Ridge Long Term Ecological Research site during the 2017 summer-snowmelt season. Visible, near-infrared and thermal-infrared imagery was collected. This unique series of 5–25 cm resolution multi-spectral and thermal orthomosaics provides a unique snapshot of seasonal transitions in a high alpine catchment. Weekly radiometrically calibrated normalised difference vegetation index maps can be used to track vegetation health at the pixel scale through time. Thermal imagery can be used to map the movement of snowmelt across and within the near sub-surface as well as identify locations where groundwater is discharging to the surface. A 10 cm resolution digital surface model and dense point cloud (146 points m-2) are also provided for topographic analysis of the snow-free surface. These datasets augment ongoing data collection within this heavily studied and important alpine site; they are made publicly available to facilitate wider use by the research community. Datasets and related metadata can be accessed through the Environmental Data Initiative Data Portal, 10.6073/pasta/dadd5c2e4a65c781c2371643f7ff9dc4 (Wigmore, 2022a), 10.6073/pasta/073a5a67ddba08ba3a24fe85c5154da7 (Wigmore, 2022c), 10.6073/pasta/a4f57c82ad274aa2640e0a79649290ca (Wigmore and Niwot Ridge LTER, 2021a), 10.6073/pasta/444a7923deebc4b660436e76ffa3130c (Wigmore and Niwot Ridge LTER, 2021b), 10.6073/pasta/1289b3b41a46284d2a1c42f1b08b3807 (Wigmore and Niwot Ridge LTER, 2022a), 10.6073/pasta/70518d55a8d6ec95f04f2d8a0920b7b8 (Wigmore and Niwot Ridge LTER, 2022b). A summary of the available datasets can be found in the data availability section below.
... In addition to 3D-reconstruction capabilities, many commercial 3D-reconstruction software packages include photogrammetry capabilities for professional use. Photoscan [79] is software that automatically generates high-quality 3D models based on images. Pix4Dmapper is standard 3D-reconstruction and aerial-photogrammetry software that includes point-cloud reconstruction, 3D-mesh reconstruction, elevation-map generation and other functions. ...
Article
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The reconstruction of realistic large-scale 3D scene models using aerial images or videos has significant applications in smart cities, surveying and mapping, the military and other fields. In the current state-of-the-art 3D-reconstruction pipeline, the massive scale of the scene and the enormous amount of input data are still considerable obstacles to the rapid reconstruction of large-scale 3D scene models. In this paper, we develop a professional system for large-scale 3D reconstruction. First, in the sparse point-cloud reconstruction stage, the computed matching relationships are used as the initial camera graph and divided into multiple subgraphs by a clustering algorithm. Multiple computational nodes execute the local structure-from-motion (SFM) technique, and local cameras are registered. Global camera alignment is achieved by integrating and optimizing all local camera poses. Second, in the dense point-cloud reconstruction stage, the adjacency information is decoupled from the pixel level by red-and-black checkerboard grid sampling. The optimal depth value is obtained using normalized cross-correlation (NCC). Additionally, during the mesh-reconstruction stage, feature-preserving mesh simplification, Laplace mesh-smoothing and mesh-detail-recovery methods are used to improve the quality of the mesh model. Finally, the above algorithms are integrated into our large-scale 3D-reconstruction system. Experiments show that the system can effectively improve the reconstruction speed of large-scale 3D scenes.
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This paper presents a quantitative comparison of several multi-view stereo reconstruction algorithms. Until now, the lack of suitable calibrated multi-view image datasets with known ground truth (3D shape models) has prevented such direct comparisons. In this paper, we first survey multi-view stereo algorithms and compare them qualitatively using a taxonomy that differentiates their key properties. We then describe our process for acquiring and calibrating multiview image datasets with high-accuracy ground truth and introduce our evaluation methodology. Finally, we present the results of our quantitative comparison of state-of-the-art multi-view stereo reconstruction algorithms on six benchmark datasets. The datasets, evaluation details, and instructions for submitting new models are available online at http://vision.middlebury.edu/mview.
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