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Globally, 13 million hectares are cleared every year, of which a significant percentage (96%) in tropical forests. In this context, on October 22, 2020, the European Parliament adopted a resolution containing recommendations to the Commission on the creation of an EU legal framework for halting and reversing global deforestation with particularities for the EU (2020/2006 (INL)). Regardless of the causes of deforestation, the main effects are climate change and, as a cumulative effect, landslides. In this paper we will present an overview of the situation of the Forest-Deforestation/Clearing-Causality relationship and effects with an emphasis on the subject - the evolution of landslides following deforestation. Also, through a case study, carried out within the GeoSES crossborder project - Extension of the operational "Space Emergency System" towards monitoring of dangerous natural and man-made geo-processes in the HU-SK-RO-UA cross-border region, HUSKROUA 1702/8.1./0065, we shall present a real case of landslide produced as a result of massive deforestation in the area, the location being the Municipality of Sighetu Marmației. [ABSTRACT FROM AUTHOR]

The paper presents an application of the methodology used in the paper "Synthetic analysis of geoinformatics technologies for cultural heritage conservation, methodological approach". The creation of the 3D model of the Rákóczi-Bánffy Castle in Urmeniș, Bistrița Năsăud County, was done by applying and integrating Terrestrial Laser Scanning (TLS) technologies and aerial photogrammetry performed with an Unmanned Aerial Vehicle (UAV). Agisoft Photoscan was used to compare the results and then they were compared with the images scanned using CloudCompare software. Thus, following the performance, with the help of the mentioned software, of a series of processing of the point cloud obtained, through the two imaging technologies, the error between the points belonging to the point cloud taken with UAV and the one taken with Laser Scanner was between 1 and 15 mm, the margin of error being acceptable for monuments without complex architectural details, so that the point cloud resulting from UAVs can be used successfully in this activity. The aim of the paper is to elaborate a geomatic methodology with an optimized cost-quality ratio, later replicable in the analysis of the current state of other constructions of the same type, knowing that over 600 castles in Transylvania alone are in a similar state, and such cases can be found in other Central European states as well. [ABSTRACT FROM AUTHOR]

There is an increase in the use of photogrammetric point clouds for tree attribute mensuration. Stem diameter and circumference can be estimated from point clouds using stem disks of varying thicknesses along the bole. However, there is a dearth of information on the effect of the thickness of point cloud-based stem disks on the accuracy of diameter and circumference estimations. In this study, we outlined a GIS-based procedure for analysing Structure from Motion-derived photogrammetric point clouds with a view to providing an optimal disk thickness for accurate circumference estimates. Geo-referenced point clouds were created from photographs of 30 trees belonging to five savanna species. For each tree, 20 horizontal stem disks, with increasing thicknesses of 1 to 20 mm were made at breast height using the open source QGIS software. The resulting cross-sections were manually delineated and digitised. The difference between reference (manually measured) and point cloud-based circumferences at breast height was expressed as mean absolute percent error (MAPE) and compared across tree species, size and disk thickness. We found significant effects of species identity, tree size and disk thickness on MAPE. A stem disk of 7 mm in thickness provided consistently lower MAPE values (< 6%). This suggests that the accuracy of tree stem circumference estimations from photogrammetric point clouds depends on stem disk thickness.

Several valuable heritage structures worldwide are in danger due to natural causes or human interferences. Therefore, a low-cost modeling technique is extremely important and widely needed for the preservation of heritage especially in poorer countries. This study evaluates the precision and accuracy of terrestrial photogrammetry via low-cost digital cameras to construct a 3-D model of an object. To obtain the goal, a building façade is imaged by employing two low-cost digital cameras, namely Canon and Pentax. The accuracy of the photogrammetric point clouds that are generated via the method is compared with a few natural control points collected via a laser total station. Cloud-to-cloud distance is computed for different 3-D models to investigate different variables such as camera type and control points. The results of the practical field experiment indicate that the mean differences between obtained 3-D models and reference points are in the range of 2.3–4.1 cm without using any control points. Using a few of the control points, the differences are improved such that they are between 1.4 and 1.6 cm. The comparisons indicate that the largest variances between the laser total station and photogrammetric outcomes occurred when the Pentax camera was used. [ABSTRACT FROM AUTHOR]

Nowadays, surveys using unmanned aerial vehicles is becoming popular. The resulting orthophotomap is the final product for creating digital plans and cardboard. The objectives of the study are to study the possibilities of obtaining orthophotomaps from survey materials using unmanned aerial vehicles based on the results of the experiment. The article describes various types of aerial photography. Some types of unmanned flying vehicles to conduct aerial photography for the purpose of monitoring, engineering surveys, inventory of agricultural land, and crop forecasts are considered. A description of aerial photography surveying is given on the example of the city of Dzerzhinsk, Minsk Region, which is performed taking into account the unmanned flying vehicles of GeoScan 201 and the Republican agricultural aero-geodesic unitary enterprise BelPSHAGI. A description of the GeoScan Planner software and basic pre-flight preparation is given. The stages of the preparatory work before the aerial photography, the creation of the planning and high-altitude geodetic justification, the implementation of aerial photography procedures, the steps of the aerial photograph anchorage procedure are considered. Agisoft Photoscan, which allows to get clouds of points, surfaces, 3D models and orthophotomaps using digital raster images are presented. The map of heights (DEM) of the terrain and the orthophotomap was made on the basis of a dense points cloud. According to the results of the research, a conclusion was made on the possibility of using aerial photography materials obtained using unmanned flying vehicles to get orthophotomaps of the required accuracy. [ABSTRACT FROM AUTHOR]

Structure from Motion (SfM) is a tool being increasingly utilised in geosciences for high-resolution three-dimensional mapping of landscapes. However, a number of authors have demonstrated that broad-scale systematic deformations, in the form of 'doming' and 'bowling', can occur when applied to linear (low-amplitude, feature-limited) topographies. In such contexts, a more rigorous lens calibration and ground control point acquisition process is required, which means that application of SfM to environments such as tidal flats or desert plains can be challenging. Uncertainties in elevation models generated through SfM were investigated here in the context of the low elevation, micro-topographic environment of saltmarsh. Eight digital surface models (DSMs) were generated for a saltmarsh site in the Deben Estuary (Suffolk, UK) using imagery acquired by a low-cost consumer grade unmanned aerial system (UAS). The results provide clear illustration of the systematic bowling effect following self-calibration during bundle adjustment. This was due to poor estimations of distortion parameters in the camera model. Deformation was most pronounced when UAS-GPS data were used for georeferencing. The use of dGPS-determined ground control points improved the DSM, but did not fully mitigate the deformations. By introducing a pre-calibrated model, derived using a typical checkerboard routine, deformation was significantly mitigated. These results were tested in both the commercial Agisoft PhotoScan® and open-source Micmac software. When self-calibration was used, Micmac generated significantly more accurate DSMs because a more complex lens distortion model could be implemented. The results show that when mapping flat topographies, pre-calibration of the camera model out-performs self-calibration. However, if pre-calibration is not possible, a complex distortion model (such as Micmac's Four model) can be utilised to limit deformation. The results of the software analysis concluded there is no one-size fits all software solution, and therefore customisable open-source systems offer many potential benefits. [ABSTRACT FROM AUTHOR]

Abstract A new methodology to identify discontinuity sets at the tunnel face based on the Structure from Motion (SfM) photogrammetric technique is proposed. The work focuses on the performance of this technique when employed to characterize the ground mass under real tunneling conditions, illustrating its possibilities and analyzing several aspects that affect the quality of the obtained results. By means of a set of overlapping photographs from the tunnel face, SfM constructs a 3D point cloud model, from which discontinuities are identified using a discontinuity set extractor software. To orientate and scale the digital model, an easy-to-use "portable orientation template", specifically developed for this work, is employed. The proposed methodology is applied to two real tunnels under construction in Northern Spain. Its results are compared with those obtained with a traditional analysis based on manual compass measurements. Results show that the SfM methodology provides an adequate characterization of the structure of the rock mass, identifying the same number of discontinuity sets as the compass measurements approach and with differences in orientation that are within the uncertainty range associated to manual measurements. Only one sub-horizontal set presented higher orientation differences, but this is mainly due to the presence of shotcrete at the face. In addition to the advantages of a "distant" measurement technique—e.g., health and safety advantages, capability to characterize unreachable areas, etc.—, as well as to the advantage of its reduced cost, the proposed SfM methodology and its associated tools allow one to represent planes associated to each discontinuity set back into the original 3D digital point model, and to perform detailed analyses that clarify and improve the obtained results. Finally, an analysis about the minimum number of photographs needed to adequately characterize the tunnel face is conducted, with results showing that around 15 good quality photographs are enough for tunnel faces with excavated areas of about 50 m2. [ABSTRACT FROM AUTHOR]

Preparing digital documentation of historical buildings is a form of protecting cultural heritage. Recently there have been several intensive studies using non-metric digital images to construct realistic 3D models of historical buildings. Increasingly often, non-metric digital images are obtained with unmanned aerial vehicles (UAV). Technologies and methods of UAV flights are quite different from traditional photogrammetric approaches. The lack of technical guidelines for using drones inhibits the process of implementing new methods of data acquisition.

Conlin, M.; Cohn, N., and Ruggiero, P., 2018. A quantitative comparison of low-cost Structure from Motion (SfM) data collection platforms on beaches and dunes. Observations of beach and dune geomorphology are critical for characterizing coastal processes and hazards. A relatively new approach for monitoring the coastline is Structure from Motion photogrammetry (SfM), a technique that uses overlapping photographs to reconstruct three-dimensional surfaces. In this study, a quantitative comparison of multiple low-cost kite-, pole-, and unmanned aerial vehicle (UAV)–based SfM data collection platforms is performed to illuminate important considerations when choosing an SfM platform for use in measuring beach and dune topography. A multicriteria analysis based on SfM results and platform usability is used to complete this comparison. Results show that UAV-based platforms received high performance scores, largely because these stable, high-flying platforms provide images with adequate texture to allow accurate three-dimensional topographic reconstruction. Although data extracted from the kite- and pole-based systems are less accurate, these platforms possess increased usability because of decreased barriers to entry and fewer environmental limitations (in the case of the pole), which increases their overall performance. These results illustrate that the overall effectiveness of a platform is based on many factors beyond vertical error of extracted data, and factors of platform usability can be important to consider when choosing an SfM platform. Furthermore, this multiplatform analysis reveals the important idea that different platforms can be optimal for different applications depending on the study site and environmental conditions. As the technology progresses, many improvements to platforms are likely to emerge, allowing SfM to become an even more useful tool for the coastal scientist. [ABSTRACT FROM AUTHOR]

Fisheye camera installed on-board mass market UAS are becoming very popular and it is more and more frequent the use of such platforms for photogrammetric purposes. The interest of wide-angles images for 3D modelling is confirmed by the introduction of fisheye models in several commercial software packages. The paper exploits the different mathematical models implemented in the most famous commercial photogrammetric software packages, highlighting the different processing pipelines and analysing the achievable results in terms of checkpoint residuals, as well as the quality of the delivered 3D point clouds. A two-step approach based on the creation of undistorted images has been tested too. An experimental test has been carried out using a Parrot Bebop 2 UAS by performing a flight over an historical complex located near Piacenza (Northern Italy), which is characterized by the simultaneous presence of horizontal, vertical and oblique surfaces. Different flight configurations have been tested to evaluate the potentiality and possible drawbacks of the previously mentioned UAS platform. Results confirmed that the fisheye images acquired with the Parrot Bebop 2 are suitable for 3D modelling, ensuring accuracies of the photogrammetric blocks of the order of the GSD (about 0.05 m normal to the optic axis in case of a flight height equal to 35 m). The generated point clouds have been compared to a reference scan, acquired by means of a MS60 MultiStation, resulting in differences below 0.05 in all directions. [ABSTRACT FROM AUTHOR]

This research paper deals with the experiences of the Group of Automation, Robotics and Perception (GARP) of the Universidad Central "Marta Abreu" de Las Villas (UCLV) and the Territorial Research Station of the Sugarcane (ETICA), in the use of an Unmanned Aerial Vehicles (UA V) for multispectral photogrammetry, with the aim at mapping experimental sugarcane plantations. Experimental tests with two of the best image processing software available at the market were done, Agisoft Photoscan and Pix4D, generating 3D orthomosaics and index maps NDVI (Normalized Difference Vegetation Index). Both programs were evaluated in terms of ease of use, processing time, and visual quality of the product, having the flight conditions of the UAV defined for an adequate processing of the images collected with the Parrot Sequoia Multispectral Camera. The results indicated a Pix4D program as the most efficient one to calculate vegetative indexes due to the incorporation of radiometric corrections specific for the orthomosaics. The results achieved were analyzed in collaboration with expert agronomists from ETICA, to make comparisons between the different groups of processed images and the correlation between the index maps with the variety of sugarcane crops, their age, the levels of plant vigor and other agricultural variables. The obtained results show that the spectral response permits to discriminate the fields depending on the age and demographic density in each parcel, but the NDVI don't facilitate the determination of different varieties with the same plantation date. [ABSTRACT FROM AUTHOR]

In this research, the issues related to processing and analysis of the images, acquired by the lowcost terrestrial sensors and an unmanned aerial vehicle (UAV) of the archaeological sites in an urban environment placed in area of Kutaisi, Georgia, have been considered. Taking into account generation of the Bagrati site photogrammetric documentation, the low-cost UAV DJI Phantom 3 and Pentax SLR camera, were chosen. Due to the geometrical and radiometric parameters of the chosen sensors, an extended methodology of UAV and terrestrial data processing in Agisoft PhotoScan was proposed. This task solution was enabled by application programming interface API (which allowed taking advantage of software functions - not available in the basic version of the program) and additionally the script written in MatLab software by authors. The method of processing, filtrating, eliminating and weighting of the measurement observations in the bundle adjustment process was proposed. As a result of performed works, the accuracy of the results of the bundle adjustment, increased significantly in comparison to the raw data. Furthermore, statistical data analysis had been expanded. [ABSTRACT FROM AUTHOR]

Since the late 20th century, new technologies have provided powerful ways to digitize biological structures in three dimensions (3D). Among those, photogrammetry is a low cost and non-destructive method, which has become increasingly used since the development of the digital camera. Recent studies have demonstrated that reconstructions of isolated elements can be of as high quality as those obtained with laser scanners. Here, we wanted to test the performance of photogrammetry for the quantitative analysis of mounted specimens in museum exhibitions. Indeed, access to material can be an issue in comparative anatomy and, especially, in paleontology. This is notably the case for large, impressive specimens. We performed reconstructions based on acquisitions done under various conditions and also tested the reconstruction performance of two software programs. The resulting 3D models were then compared to a reference object corresponding to the bone of interest digitized with a cutting-edge surface scanner. Our results show that photogrammetry enables quality reconstruction of the almost entire surface of the mounted bone of interest. Photogrammetry thus appears a reliable method perfectly suited to study large specimens exposed in museum gallery. [ABSTRACT FROM AUTHOR]

The ecological monitoring of threatened species is vital for their survival as it provides the baselines for conservation, research and management strategies. Wildlife studies using tracks are controversial mainly due to unreliable recording techniques limited to two-dimensions (2D). We assess close-range photogrammetry as a low-cost, rapid, practical and reliable field technique for the digital three-dimensional (3D) modelling of lion Panthera leo paws and tracks. First, we tested three reconstruction parameters affecting the 3D model quality. We then compared direct measurements on the paws and tracks versus the same measurements on their digital 3D models. Finally, we assessed the minimum number of photographs required for the 3D reconstruction. Masking, auto-calibration and optimization provided higher reconstruction quality. Paws masked semi-automatically and tracks masked manually were characterized by a geometric deviation of 0.23 ± 0.18 cm and 0.50 ± 0.33 cm respectively. Unmasked tracks delineated by means of the contour lines had a geometric deviation of −0.06 ± 0.39 cm. The use of a correction factor reduced the geometric deviation to −0.03 ± 0.20 cm (pad-masked paws), −0.04 ± 0.35 cm (pad-masked tracks) and −0.01 ± 0.39 cm (unmasked tracks). Based on the predicted error, the minimum number of photographs required for an accurate reconstruction is seven (paws) or eight (tracks) photographs. This field technique, using only a digital camera and a ruler, takes less than one minute to sample a paw or track. The introduction of the 3D facet provides more realistic replications of paws and tracks that will enable a better understanding of their intrinsic properties and variation due to external factors. This advanced recording technique will permit a refinement of the current methods aiming at identifying species, age, sex and individual from tracks. [ABSTRACT FROM AUTHOR]

This paper aims to provide a method of constructing and testing the accuracy of a three dimensional (3D) model for non-metric camera images using Agisoft PhotoScan to solve the problems regarding large investment, long processing periods and high technical difficulties. On the basis of data pre-processing, this software presents a way of orientating data, extracting point clouds, building Triangulated Irregular Networks (TIN), Digital Elevation Models (DEM) and producing Digital Orthophoto Maps (DOM). From these networks, a 3D model of the research area can be established. The experimental results show a highly precise 3D model can be rapidly established using this method. The construction time is shortened and the relevant investment required to produce the map is reduced. This method is a robust and relatively quick approach to build 3D models which is relevant for many applications. [ABSTRACT FROM AUTHOR]

Preparing digital documentation of historical buildings is a form of protecting cultural heritage. Recently there have been several intensive studies using non-metric digital images to construct realistic 3D models of historical buildings. Increasingly often, non-metric digital images are obtained with unmanned aerial vehicles (UAV). Technologies and methods of UAV flights are quite different from traditional photogrammetric approaches. The lack of technical guidelines for using drones inhibits the process of implementing new methods of data acquisition. This paper presents the results of experiments in the use of digital images in the construction of photo-realistic 3D model of a historical building (Raphaelsohns' Sawmill in Olsztyn). The aim of the study at the first stage was to determine the meteorological and technical conditions for the acquisition of aerial and ground-based photographs. At the next stage, the technology of 3D modelling was developed using only ground-based or only aerial non-metric digital images. At the last stage of the study, an experiment was conducted to assess the possibility of 3D modelling with the comprehensive use of aerial (UAV) and ground-based digital photographs in terms of their labour intensity and precision of development. Data integration and automatic photo-realistic 3D construction of the models was done with Pix4Dmapper and Agisoft PhotoScan software Analyses have shown that when certain parameters established in an experiment are kept, the process of developing the stock-taking documentation for a historical building moves from the standards of analogue to digital technology with considerably reduced cost. [ABSTRACT FROM AUTHOR]

Our understanding of Earth surface processes is rapidly advancing as new remote sensing technologies such as LiDAR and close-range digital photogrammetry become more accessible and affordable. A very-high spatial resolution digital terrain model (DTM) and orthophoto mosaic (mm scale) were produced using close-range digital photogrammetry based on ‘Structure-from-Motion’ (SfM) algorithms for a 250 m transect along a shallow coral reef flat on Heron Reef, Great Barrier Reef. The precise terrain data were used to characterise surface roughness, a critical factor affecting ecological and physical processes on the reef. Three roughness parameters, namely the root mean square height, tortuosity (or rugosity) and fractal dimension, were derived and compared in order to asses which one better characterises reef flat roughness. The typical relief across the shallow reef flat was 0.1 m with a maximum value of 0.42 m. Coral reef terrain roughness, as characterised by the three chosen parameters, generally increased towards the middle of the transect where live coral covers most of the reef flat and decreases towards the edges of the transect. The fractal dimension (values ranging from 2.2 to 2.59) best characterised reef roughness, as evidenced by a closer agreement with the distribution of known coral benthic substrates. This is the first study quantifying scale-independent roughness of a coral reef at benthic and biotope/patch levels (cm-m). The readily available and cost-effective methods presented are highly appropriate for data collection, processing and analysis to generate very-high spatial resolution DTMs and orthophoto mosaics of shallow and energetic coral reefs. [ABSTRACT FROM AUTHOR]

The application of close-range photogrammetry for 3D model reconstruction based on photographs taken with calibrated amateur cameras is opening new ways in the documentation, presentation and preservation of archeological artefacts and represents an alternative, low-cost approach to traditional solutions. As a part of the workshop organized by the Faculty of Geodesy in collaboration with the Faculty of Humanities and Social Sciences, photographs of a prehistoric double bowl replica from Mikanovac region were processed using the Agisoft PhotoScan software. The final result of the 3D reconstruction is a highly-detailed textured 3D model of the artifact. [ABSTRACT FROM AUTHOR]

Computer Vision Photogrammetry allows archaeologists to accurately record underwater sites in three dimensions using simple two-dimensional picture or video sequences, automatically processed in dedicated software. In this article, I share my experience in working with one such software package, namely PhotoScan, to record a Dutch shipwreck site. In order to demonstrate the method's reliability and flexibility, the site in question is reconstructed from simple GoPro footage, captured in low-visibility conditions. Based on the results of this case study, Computer Vision Photogrammetry compares very favourably to manual recording methods both in recording efficiency, and in the quality of the final results. In a final section, the significance of Computer Vision Photogrammetry is then assessed from a historical perspective, by placing the current research in the wider context of about half a century of successful use of Analytical and later Digital photogrammetry in the field of underwater archaeology. I conclude that while photogrammetry has been used in our discipline for several decades now, for various reasons the method was only ever used by a relatively small percentage of projects. This is likely to change in the near future since, compared to the 'traditional' photogrammetry approaches employed in the past, today Computer Vision Photogrammetry is easier to use, more reliable and more affordable than ever before, while at the same time producing more accurate and more detailed three-dimensional results. [ABSTRACT FROM AUTHOR]

Abstract: Archaeological practice within the European context of heritage management is facing huge challenges in ways of recording and reproduction of ex-situ preserved sites. As a consequence of the Valletta-treaty, numbers of archived images and drawings of excavated structures as prime sources of past human activity, are exponentially growing. Contrarily to portable remains however, their future study and revision is biased by the two-dimensional character of the recorded data, rendering difficult their future reconstruction for new study or public dissemination. A more realistic three-dimensional (3D) way of recording and archiving should be pursued. In this paper the possibilities for 3D registration of archaeological features are examined in a computer vision-based approach using the PhotoScan software package (Agisoft LCC). It proved to be a scientific and cost-effective improvement compared to traditional documentation methods. Advantages can be found in the high accuracy and straightforwardness of the methodology. The extraction of an orthophoto or a Digital Terrain Model from the 3D model makes it feasible to integrate detailed and accurate information into the digital archaeological excavation plan. The visual character of 3D surface modeling offers enhanced output-possibilities allowing a better documentation of in-situ structures for future research and a higher public participation and awareness for the archaeological heritage. [Copyright &y& Elsevier]

Not so long ago, photogrammetry was rarely used geodetic method. In most cases, it was used for the purposes of creating state digital orthophoto. This long-term and labored procedure was only done by the biggest geodetic offices in the country. With the development of very powerful computers and photogrammetric softwares, processing of these kind of data became much simpler and faster, while the final results reached an impressive level of accuracy. This paper describes the method of using panoramic images created with Trimble S7 Vision total station and the reconstruction of 3D model based on the photos filmed by UAV (Unmanned Aerial Vehicle) Falcon 8 Trinity. It also goes through the procedure of relative static observation post-processing and computing of the geodetic points coordinates as well as coordinates of markers on identical points based on the total station observations. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV) and structure from motion (SfM) photogrammetry techniques are widely used for field-based, high-throughput plant phenotyping nowadays, but some of the intermediate processes throughout the workflow remain manual. For example, geographic information system (GIS) software is used to manually assess the 2D/3D field reconstruction quality and cropping region of interests (ROIs) from the whole field. In addition, extracting phenotypic traits from raw UAV images is more competitive than directly from the digital orthomosaic (DOM). Currently, no easy-to-use tools are available to implement previous tasks for commonly used commercial SfM software, such as Pix4D and Agisoft Metashape. Hence, an open source software package called easy intermediate data processor (EasyIDP; MIT license) was developed to decrease the workload in intermediate data processing mentioned above. The functions of the proposed package include (1) an ROI cropping module, assisting in reconstruction quality assessment and cropping ROIs from the whole field, and (2) an ROI reversing module, projecting ROIs to relative raw images. The result showed that both cropping and reversing modules work as expected. Moreover, the effects of ROI height selection and reversed ROI position on raw images to reverse calculation were discussed. This tool shows great potential for decreasing workload in data annotation for machine learning applications. [ABSTRACT FROM AUTHOR]