Agisoft Metashape Research Articles

THE EVALUATION OF STRUCTURE-FROM-MOTION WORKFLOW WITH THE TLS SYNTHETIC IMAGES SIMULATOR – THE CULTURAL HERITAGE APPROACH

Abstract. Modern measurement technologies such as Terrestrial Laser Scanning or combined Structure-from-Motion with Multi-View Stereo are commonly utilised to monitor, preserve and document cultural heritage objects and sites. For this reason, it is essential to know the capabilities and limitations of the sensor used, the data processing methods, and in particular, the orientation of the images. However, these algorithms tackle different errors and have different effects on the final accuracy of images orientation. For this reason, it is essential to know how the algorithms implemented in the Structure-from-Motion approach work. Due to the impossibility of obtaining this information for commercial solutions, it is necessary to use synthetic data to assess the quality of the SfM process. Therefore, this article aims to present the method of evaluation of SfM approach implemented in commercial Agisoft Metashape and COLLMAP open-source software based on the synthetic data generated from TLS point clouds of three different Cultural Heritage sites. In addition, obtained results were compared with the author's SfM approach based on BRISK, FAST, CenSurE, SIFT and SURF (and its Affine detectors equivalents) detector implemented (Fig. 1) and Learned-based -feature extraction approach SuperGlue and LoFTR. The second aim of this research is to propose an application to automatically generate scalable benchmark based on point clouds or 3D models of cultural heritage objects.

LESSONS LEARNT FROM THE HIGH RESOLUTION UAS PHOTOGRAMMETRIC SURVEY OF A HISTORIC URBAN AREA: UNESCO SITE OF SABBIONETA

Abstract. In view of the increasing development of the smart city concept and the generation of 3d city models, it becomes essential to have an up-to-date, high-detail 3D survey of urban areas. There are several technologies that enable the development of a geometric survey of urban areas, including the use of aerial laser scanning, remote sensing, mobile mapping systems, and Unmanned Aerial Sistems (UAS) photogrammetry. Of these, the last mentioned, when developed with high-resolution cameras and flight plans with appropriate elevations, allows point clouds to be obtained at a high level of detail and orthophotos with great resolution. This technique may be the preferable choice when the object of the survey is a historic urban area, which has some special features, which might make surveying difficult with other surveying techniques. This paper presents the survey with UAS photogrammetry of a historic urban area: the city of Sabbioneta, in northern Italy. The UAS flight planning is discussed in details, specifically referring to european UAS flight regulations. The survey was developed with DJI Matrice 300 RTK, equipped with a flight terminator and parachute, and coupled with a high precision GNSS Mobile Station DJI D-RTK 2. Ground control points and check points were measured with GNSS receiver Leica GS18. Images were processed with Agisoft Metashape following a photogrammetric workflow. The resulting orthophoto has a pixel size of 1 cm. The obtained dense point cloud is suitable for future use for its segmentation by testing existing machine learning and deep learning methods and for future urban analysis.

FAST AND ACCURATE DOCUMENTATION OF ARCHITECTURAL HERITAGE WITH LOW-COST SPHERICAL PANORAMIC PHOTOGRAPHS FROM 360 CAMERAS

Abstract. This research wants to show the possibility of quickly making high-quality photogrammetric models using 360-degree panoramic photographs, but made using low-cost, single-shot cameras. Currently there is a wide variety of single shot cameras, in which the shape of the camera can vary according to the number of lenses that it incorporates in the camera mount, but this will directly affect the quality of the photography. result and in the price of the team.The fundamental characteristic of single-shot cameras is that they are capable of capturing a 360-degree panoramic photo at the very moment of shooting, which allows to greatly reduce data collection times compared to the normal method of taking photos spherical. This occurs thanks to the fact that they have several lenses that allow them to capture everything that happens around them in a fraction of a second. In addition, the composition times of the final image are also reduced, since they incorporate a processor that allows them to stitch the panorama automatically. These features make data capture very fast, greatly reducing work times.To demonstrate the efficiency of this equipment, several tests have been carried out in different spaces, interior and exterior, of the Cathedral of Plasencia. For each data set, the object documentation was performed twice. The first time it was done with a Faro Focus 3D laser scanner to generate the highly metrically accurate control model. And the second time a Xiaomi Mi Sphere camera was used to generate the comparison model. The photogrammetric models were processed with the Agisoft Metashape software and the comparison of the models in the CloudCompare software.The results obtained in these comparisons have been very promising, showing the effectiveness of these cameras to quickly document heritage. All the data on working times, geometric precision of the models, metric deviations, etc. They are shown below in the document.

A METHOD FOR ESTIMATING THE ACCURACY OF THE TIE POINTS CLOUD: THE CASE STUDY OF PALAZZO DE FALCO

Abstract. In the context of cultural heritage documentation and conservation, an accurate 3D model is essential to properly describe an artifact of historical relevance and provide the expert user with verified metric data. In this paper we propose a workflow aimed at estimating errors in the image orientation steps, which is useful for improving the accuracy of the sparse cloud (composed of Tie Points). Some parameters provided as input to the processing software, often overlooked by the user in favour of the default ones, are analysed. Specifically, tests are carried out using the commercial software package Agisoft Metashape and involve the analysis of three parameters: (i) the accuracy of measuring the Ground Control Points (GCPs) provided by the user; (ii) the accuracy of the Tie Points (TPs) computed by the software; and (iii) the accuracy of collimating the GCPs on the image. The accuracy of the GCPs is estimated by implementing the formulas of error propagation in MATLAB, considering the three concurring sources of error: the coordinate measurement with the Total Station (TS), the coordinate transformation from the local system to the UTM/ETRF00 System, and the GNSS measurement for estimating the transformation parameters. The transformation parameters are calculated using the Bursa Wolf method. The collimation accuracy of GCPs on the image is estimated by the reprojection error of each single GCPs on the image plane. The accuracy of the GCPs will be estimated by the standard error per unit weight (SEUW), accurate GCPs being expected to have a SEUW value close to unity. SEUW is also the overall indicator for estimating the accuracy of the TPS cloud because it is influenced, in different ways, by all three parameters analysed. Test Area is a historic building located in the town of Fisciano, a few kilometres from the city of Salerno, known as Palazzo De Falco. The results highlight how these parameters, if not properly considered, can significantly affect the final 3D model.

Identifying the Optimal Radiometric Calibration Method for UAV-Based Multispectral Imaging

The development of UAVs and multispectral cameras has led to remote sensing applications with unprecedented spatial resolution. However, uncertainty remains on the radiometric calibration process for converting raw images to surface reflectance. Several calibration methods exist, but the advantages and disadvantages of each are not well understood. We performed an empirical analysis of five different methods for calibrating a 10-band multispectral camera, the MicaSense RedEdge MX Dual Camera System, by comparing multispectral images with spectrometer measurements taken in the field on the same day. Two datasets were collected, one in clear-sky and one in overcast conditions on the same field. We found that the empirical line method (ELM), using multiple radiometric reference targets imaged at mission altitude performed best in terms of bias and RMSE. However, two user-friendly commercial solutions relying on one single grey reference panel were only slightly less accurate and resulted in sufficiently accurate reflectance maps for most applications, particularly in clear-sky conditions. In overcast conditions, the increase in accuracy of more elaborate methods was higher. Incorporating measurements of an integrated downwelling light sensor (DLS2) did not improve the bias nor RMSE, even in overcast conditions. Ultimately, the choice of the calibration method depends on required accuracy, time constraints and flight conditions. When the more accurate ELM is not possible, commercial, user-friendly solutions like the ones offered by Agisoft Metashape and Pix4D can be good enough.

Spatio-Temporal Analysis of Ground Movement Using Unmanned Aerial Vehicle Photogrammetry in Gampong Lamkleng, Aceh Besar

Ground movement is one of the most frequent disasters causing major damages in Indonesia. Unmanned Aerial Vehicle (UAV) has been widely used as a rapid observation method to obtain detailed characterization of ground movement. Often, active landslide area is difficult to access. This hinders close monitoring and observations of the ground movement. This study aims to demonstrate the use of UAV as tools for monitoring and observations on active ground movement area and to validate the results. For this purpose, the study was conducted at Gampong Lamkleng, Aceh Besar-Indonesia using spatio-temporal analysis by UAV photogrammetry. The UAV was chosen because it is easy to use, practical, and safe for landslide area that are relatively small and difficult to reach. Aerial photographs were processed using the Agisoft Metashape software in modeling and analyzed using Quantum GIS (QGIS) and ArcGis. The observation results show that the largest ground movement occurred in January 20 to 23, 2021 which was related to precipitation rates measured at a nearby rainfall station. The movement volume was 1,411.063 m3 and a rate of ground movement reaching 0.69 m/day due to heavy rain. The estimated value of losses is IDR 1,055,854,000. The UAV images analysis were compared to actual ground elevation measured using Real-Time Kinematic (RTK). The validation show that the accuracy based on comparison between photogrammetric and RTK measurement was at agreeable rate (99%). Otherwise, the accuracy performed on 19 check point using Root Mean Square Error analysis found that the accuracy was still very low. The low RMSE value is due to the georeferencing process using the Ground Control Point not being carried out.

Analysis of Vegetation Index of Oil Palm Plants infected with Ganoderma Disease

One of the characteristics of Ganoderma disease is that it is asymptomatic, visual symptoms appear when the condition of the plant is severe so early detection and identification become a fundamental problem. This study aims to identify Ganoderma disease by analyzing the vegetation index NDVI, GNDVI, and SAVI based on the reflectance value of oil palm plant images recorded with a UAV vehicle equipped with a multispectral sensor 3 bands red (Red), green (Green), infrared (Near Infra Red) at 660nm, 550nm and 850nm wavelengths. The software used is Mission Planner, Agisoft Meta Shape, Mapir Camera Control, ArcGIS 10.5, and ENVI 5.3. The research location is in an oil palm plantation in Pabatu in an area of 247ha planted in 2004 and 2005. The results of observations of Ganoderma disease reached 24.1%. The reflectance value of infected plants was lower than that of healthy plants with a ratio of 56.7%, 66.5%, and 44.7% in the R, G, and NIR bands. The reflectance value consistently decreases with an increasing attack of Ganoderma disease. The NDVI, GNDVI, and SAVI values in healthy plants were 0.29; 0.34, and 0.21, and in infected plants the values were lower. Vegetation index parameters can be important information to detect and identify Ganoderma disease attacks.

Smartphone-based Data Acquisition Method for Modelling 3D Printed Arm Casts

In recent years, 3D printed arm casts can replace traditional arm casts to treat bones fractures. 3D printed arm cast modelling often uses professional 3D scanning systems to capture 3D data of the arm. These systems are very expensive and may not be available in many hospitals. In order to over-come this disadvantage, inexpensive methods should be developed. This paper introduces a new data collection method based on smartphones. The photos of an arm were taken with a smartphone cam-era using some special techniques that could facilitate the process of image processing and 3D mod-elling in Agisoft Metashape and CATIA. To validate the proposed method, the photogrammetric model was compared with the scanned model (obtained by a low cost scanner) in GOM Inspect. Be-sides, a fit check of real 3D printed arm casts attached on the volunteer's forearm was also per-formed. The test results indicate that the photogrammetric model could be used as raw data for 3D arm modelling.

Geomatic Data Fusion for 3D Tree Modeling: The Case Study of Monumental Chestnut Trees

In recent years, advancements in remote and proximal sensing technology have driven innovation in environmental and land surveys. The integration of various geomatics devices, such as reflex and UAVs equipped with RGB cameras and mobile laser scanners (MLS), allows detailed and precise surveys of monumental trees. With these data fusion method, we reconstructed three monumental 3D tree models, allowing the computation of tree metric variables such as diameter at breast height (DBH), total height (TH), crown basal area (CBA), crown volume (CV) and wood volume (WV), even providing information on the tree shape and its overall conditions. We processed the point clouds in software such as CloudCompare, 3D Forest, R and MATLAB, whereas the photogrammetric processing was conducted with Agisoft Metashape. Three-dimensional tree models enhance accessibility to the data and allow for a wide range of potential applications, including the development of a tree information model (TIM), providing detailed data for monitoring tree health, growth, biomass and carbon sequestration. The encouraging results provide a basis for extending the virtualization of these monumental trees to a larger scale for conservation and monitoring.

Photogrammetry Technology by Using DJI Phantom 4 RTK in Batang Mahat, Lima Puluh Kota Regency West Sumatera

Technological developments in the field of engineering have increased rapidly. The use of geospatial information becomes one of the bases for decision-making related to planning, managing, and evaluating a field, especially in engineering, which includes the field of measurement and making topographic maps or Digital Elevation Model (DEM). High-resolution geospatial information can create a high-resolution Digital Elevation Model (DEM) map that can be very useful in making models or maps of flood-affected areas. This research will use the photogrammetry technology with DJI Phantom 4 RTK to create the DEM data of Batang Mahat located in Lima Puluh Kota Regency, West Sumatra Province. 28 flights at predetermined points had carried out to measure the area of about 9 km2. All the results of photos captured by the drone will be imported to Agisoft Metashape 1.8.2 software to create the DEM data. The DEM was then compared with DEM data from DEMNAS and the measurement data of Batang Mahat by the SDABK office. The result shows that photogrammetry technology using DJI Phantom 4 RTK compared to measurement data and DEMNAS have a similar ground elevation but different river elevation. This is because the photogrammetry by using DJI Phantom 4 RTK is not equipped with LiDAR. An alternative to solve the problem is by combining the DEM data by DJI Phantom 4 RTK with data from terrestrial surveys. However, this method is quite expensive and ineffective in analyzing flood inundation compared to DEM data (8 m resolution) from DEMNAS.

Unmanned Aerial Photography Futures to explore surface deformations and their visualization on the geoportal “ActiveTectonics”

On the example of the Rita River delta and alluvial fan of the Shartlai River located on the northwestern coast of Lake Baikal, we show the possibilities of ultra-detailed aerial photography, which allows tracing surface discontinuities with displacements from a few centimeters. The software package "Agisoft Metashape" was applied for analyzing the multi-temporal digital elevation models with the same spatial resolution of 1,67 cm/pixel to fix possible changes in the earth's surface over the year for the local area of earthquake-induced ground failures at Cape Rytyi. It has been established that most of this part has sunk by an average of 5–10 cm per year, and in the axial parts of the faults, subsidence has reached 33 cm. The greatest accumulation of sediments (up to 40 cm thick in some places) occurred on the shore, which is mainly due to the geological activity of the waves of Lake Baikal. Based on the relationship between ruptures and alluvial fans of different ages, we concluded at least two rupturing paleoearthquakes at Cape Shartlai. On the author's geoportal "ActiveTectonics", we uploaded some materials of unmanned aerial photography and geological objects in the form of orthophotomaps, digital elevation models and 360° panoramas that significantly expands the possibilities of data perception which are the basis for scientific results and conclusions.

Creating a Digital 3D Model of the Dental Cast Using Structure-from-Motion Photogrammetry Technique

Photogrammetry is a technique used to obtain a reliable database of any physical object, by creating a digital 3d model using multiple photos taken at different angles around the object. Recently, several fields have used this technique to build digital 3D models, such as topography, architecture, engineering, and medicine. Many recent dentistry studies have used the Structure-from-motion (SfM) Photogrammetry technique to reconstruct a digital three-dimensional (3D) model of a dental cast as an alternative to conventional scanning. In this research, the dental casts are constructed by applying the SfM Photogrammetry technique in which a guide to stepwise workflow is provided by utilizing simple tools which are: a smartphone camera, homemade photo studio setup, and Agisoft Metashape software. The agreements between the generated models and the reference dental casts are assessed using the Bland Altman method by calculating the mean value differences. All the calculated differences are not statistically significant (P-value >0.05), and they are also clinically accepted as the range of the mean differences (-0.042 to 0.355) is less than 0.5mm. this demonstrates that the resulted 3D models closely approximate the overall geometry of the dental casts.

Super-Resolution Techniques in Photogrammetric 3D Reconstruction from Close-Range UAV Imagery

Current Multi-View Stereo (MVS) algorithms are tools for high-quality 3D model reconstruction, strongly depending on image spatial resolution. In this context, the combination of image Super-Resolution (SR) with image-based 3D reconstruction is turning into an interesting research topic in photogrammetry, around which however only a few works have been reported so far in the literature. Here, a thorough study is carried out on various state-of-the-art image SR techniques to evaluate the suitability of such an approach in terms of its inclusion in the 3D reconstruction process. Deep-learning techniques are tested here on a UAV image dataset, while the MVS task is then performed via the Agisoft Metashape photogrammetric tool. The data under experimentation are oblique cultural heritage imagery. According to results, point clouds from low-resolution images present quality inferior to those from upsampled high-resolution ones. The SR techniques HAT and DRLN outperform bicubic interpolation, yielding high precision/recall scores for the differences of reconstructed 3D point clouds from the reference surface. The current study indicates spatial image resolution increased by SR techniques may indeed be advantageous for state-of-the art photogrammetric 3D reconstruction.

Efficient generation of occlusion-aware multispectral and thermographic point clouds

The reconstruction of 3D point clouds from image datasets is a time-consuming task that has been frequently solved by performing photogrammetric techniques on every data source. This work presents an approach to efficiently build large and dense point clouds from co-acquired images. In our case study, the sensors co-acquire visible as well as thermal and multispectral imagery. Hence, RGB point clouds are reconstructed with traditional methods, whereas the rest of the data sources with lower resolution and less identifiable features are projected into the first one, i.e., the most complete and dense. To this end, the mapping process is accelerated using the Graphics Processing Unit (GPU) and multi-threading in the CPU (Central Processing Unit). The accurate colour aggregation in 3D points is guaranteed by taking into account the occlusion of foreground surfaces. Accordingly, our solution is shown to reconstruct much more dense point clouds than notable commercial software (286% on average), e.g., Pix4Dmapper and Agisoft Metashape, in much less time (−70% on average with respect to the best alternative).

The Church of Pobeten in the XIV–XV centuries: historical and virtual reconstruction

The purpose of our work is to study the history and virtual reconstruction of the church of Pobeten, an object of historical and cultural heritage of the XIV-XV centuries. The method of analogy, creation of a digital model, photogrammetry, methods of historical informatics were used in the work. Special attention is paid to the history of the church of Pobeten and the work on creating its virtual copy. It describes working with various tools (Agisoft Metashape, Sculptris Alpha, Geomagic Studio and Sketch Up) to create photogrammetric and three-dimensional models of a historical object of the XIV century. The possibilities of using photogrammetry and three-dimensional modeling methods in the synthesis to create a virtual reconstruction of the Pobeten church are considered. The result of the work was the receipt of versatile historical data about the church of Pobeten and a virtual three-dimensional model based on them, which has the ability to edit: it can be supplemented with various elements, as well as integrated into larger works. The scope of application of the work and the results obtained can be historical local lore, preservation of objects of historical heritage, the use of the resulting product in museum installations. An interdisciplinary approach in historical research combined with computer science methods, specifically with three-dimensional computer modeling, provides exceptional opportunities, especially with the growth of information technology development, and is an actual tool of historical research in modern science.

Efficient large-scale oblique image matching based on cascade hashing and match data scheduling

In this paper, we design an efficient large-scale oblique image matching method. First, to reduce the number of redundant transmissions of match data, we propose a novel three-level buffer data scheduling (TLBDS) algorithm that considers the adjacency between images for match data scheduling from disk to graphics memory. Second, we adopt the epipolar constraint to filter the initial candidate points of cascade hashing matching, thereby significantly increasing the robustness of matching feature points. Comprehensive experiments are conducted on three oblique image datasets to test the efficiency and effectiveness of the proposed method. The experimental results show that our method can complete a match pair within 2.50∼2.64 ms, which not only is much faster than two open benchmark pipelines (i.e., OpenMVG and COLMAP) by 20.4∼97.0 times but also have higher efficiency than two state-of-the-art commercial software (i.e., Agisoft Metashape and Pix4Dmapper) by 10.4∼50.0 times.

Implementation of UAV for Pavement Functional Performance Assesment

Pavement conditions could be degraded throughout its service life. Hence, a pavement management system is needed to ensure pavement performance according to its design life. To support a reliable pavement, a pavement condition survey needs to be conducted most effective and practical way. One of the technologies used in pavement condition surveys is the Unmanned Aerial Vehicle (UAV) or known as drone. The use of UAVs for road maintenance will reduce the cost and time and with the 3D model, the accuracy level is at the centimeter level which indicates UAVs are an excellent and promising tool for road work.In this study, a PCI method of pavement condition evaluationwill be used to asses pavement through both manually surveyed and 3D model calculation with the use of Agisoft application. Later on, statistical test will be carried out such as ANOVA and correlation to determine the relationship between pavement condition obtained from two different survey method as well as the comparison in identifying pavement distresss, PCI value and pavement condition. In result, those two methods can identify identical types of damage, with a fairly high percentage of > 60%. While, manual method could identify a higher percentage of degree of severity than 3D model with the help of application. Themanual of pavement condition assessment can identify in more detail than the Agisoft Metashape application. Based on statistical tests,the two methods used show a close and unidirectional relationship.

A CRITERION OF RADIAL DISTORTION ON STRUCTURE FROM MOTION WITH CONSUMER-GRADE CAMERAS

Abstract. Images from consumer-grade cameras typically contain significant radial distortions, resulting in less accurate photogrammetry results generated using Structure from Motion (SfM). It is prone to reconstruct inaccurate scene points, becoming the so-called doming effect. The main reason is that in bundle adjustment, the last step of SfM, radial distortion is insufficiently estimated even though self-calibrating bundle adjustment was carried out. This paper designed a criterion to measure the radial distortion before SfM calculation, called Criterion on Radial Distortion (CRD). Firstly, the feature points were extracted and matched on the image; then, the image was divided into circular blocks, and the fundamental matrices were estimated by the matching points in different ring sub-blocks; finally, the difference between these fundamental matrices was used to reflect the radial distortion. Experiments on simulation data show that CRD can accurately reflect the radial distortion, which verifies its validity. Using actual UAV image data to conduct SfM experiments, CRD is consistent with the self-calibration results of Agisoft Metashape. After evaluating the accuracy of the elevation of scene points, it verifies its necessity for SfM.

THE APPLICATION OF SMARTPHONE BASED STRUCTURE FROM MOTION (SFM) PHOTOGRAMMETRY IN GROUND VOLUME MEASUREMENT

Abstract. The purpose of this research study is to assess the potential using smartphone camera captured images for 3D model reconstruction by using Structure from Motion (SFM) photogrammetry technique, specifically in term of volumetric measurement. In past, the volumetric measurement of surface or object is by using Imaging Station or by professional Terrestrial Laser Scanner (TLS), however such approach is expensive in labour fees and instruments fee respectively. A cheaper alternative is necessary for researcher and industrial to construct 3D model with greater cost efficiency. The improvement of photography and computer vision has introduced the technique of SFM photogrammetry, an alternative in 3D model reconstruction other than TLS. Non-metric camera sensor mounted inside budget smartphone are used to capture images of stockpile and processed by Agisoft Metashape Professional (AMP) software to construct a 3D model. The volumetric measurement is executed and compare with the benchmark which is the model constructed from TLS. Statistics and tables are used to indicate the accuracy of Smartphone based SFM photogrammetry in intuitive manner. The result shows that the volumetric measurement by using smartphone SFM method has significant difference when compared with the benchmark, TLS solution.

TECHNOLOGICAL SCHEMES OF MONITORING OF CULTURAL HERITAGE OBJECTS ACCORDING TO UAV SHOOT DATA

In the last few years, intensive measures have been taken to monitor and inventory the cultural heritage of Ukraine. An important aspect is the preservation of such objects and their transmission to future generations. It is important to use such a methodology and technology when performing monitoring works, which in the future will make it possible to perform a number of other tasks, in relation to a certain specific object, based on previously obtained data. Therefore, this paper proposes a method of cultural heritage monitoring using UAV-filming. As a result, the filming technology is described and technological schemes for the use of unmanned aerial vehicles for monitoring cultural heritage objects are proposed. It is obvious that the result of UAV shooting is a cloud of points, as a starting point for further processing and solving issues not only of monitoring such an object, but also of filling the national infrastructure with geospatial data, creating drawings for the reconstruction of the object, and a number of other issues. which can be realized by having a cloud of points of a certain object.
 The paper proposes the application of IDEF0-diagram methodology in the BPwin (AllFusion Process Modeler) program. A technological scheme for the use of UAVs for monitoring cultural heritage objects was created, a detailed description of each process was carried out, since the structure of the IDEF0 diagram allows creating a large number of decompositions, and a scheme for processing the shooting in the AgiSoft Metashape software complex was developed.