Search

The development of modern surveying methods, particularly, Terrestrial Laser Scanning (TLS), has found wide application in protecting and monitoring engineering and objects and sites of cultural heritage. For this reason, it is crucial that several factors a˛ecting the correctness of point cloud registration are considered, including the correctness of the distribution of control points (both signalised and natural), the quality of the process, and robustness analysis. The aim of this article is to evaluate the quality and correctness of TLS registration based on point clouds converted to raster form (in spherical mapping) and hand-crafted detectors. The expanded Structure-from-Motion (SfM) was used to detect the tie points for TLS registration and reliability assessment. The results demonstrated that affine detectors are useful in detecting a high number of key points (increased for point detectors by 8–12 times and for blob detectors by about 10–24 times), improving the quality and TLS registration completeness. For the registration accuracy of point cloud on signalised check points, the lower values can be noted for maximum RMSE errors for blob affine detectors than detectors and larger values for corner detectors and affine detectors (not more than 4 mm in the extreme cases, typically 2 mm). The commonly-applied target-based registration method yields similar results (di˛erences do not exceed – in extreme cases – 3.5 mm, typically less than 2 mm), proving that using affine detectors in the TLS registration process is and reasonable and can be recommended.

Projection of a complicated geometry of industrial objects is the complex issue, which requires properly planned and prepared measurements. Such objects must be accurately inventoried, but their complicated nature often makes the access and the visibility of their entire surface very difficult. Documentation of measurements is often prepared in the form of sketches, plans or maps, which are amended with photographic documentation. The objective of this paper is to test the possibilities to apply laser scanning and the network of digital images for inventory and monitoring of technical conditions of industrial objects. Processing of a precise documentation acquired basing on terrestrial laser scanning data or dense points clouds generated from digital images still causes many difficulties and problems. Although data processing algorithms have been intensively developed with respect to generation of high resolution orthoimages or precise vector drawings, the existing problems are still connected with limitations related to imperfections of both techniques of measurements.

This article describes the results of the project to reconstruct a Lusatian culture fortified settlement at Biskupin (one of the most well‐known archaeological sites in Poland) using various archival data. This research work will cover Site 4 at Biskupin, based on the archaeological examinations conducted there during the period 1934–1939, i.e. pre‐war photographs acquired from different heights, e.g. from a captive balloon (maximum height up to 150 m) from a blimp (at a height of 50 to 1000/1100 m) and from an aeroplane (at a height of 200 m, 300 m and up to 3 km). Modern technology enables the creation of true orthophotomaps, which are used to amend the missing drawing documentation created in situ during pre‐war archaeological excavations. The orientation of archival, non‐metric photographs acquired from different flight heights for interpretation purposes (but not for metric documentation purposes) was performed using both structure‐from‐motion algorithms (implemented in the Agisoft PhotoScan software) and the conventional approach based on Gruber points. The investigated area was divided into four sections and all the images were orientated in one reference system, which was defined during the surveys and excavations. The estimated orientation accuracy at the check points was in the range of 0.1 to 0.4 m. The final true orthophotomaps, with reference to the maintained vector drawing, were analysed. The estimated relative error was smaller than 3%. The photogrammetric products will allow for a better understanding of construction as a whole, and for the recognition of particular structures, in particular, by taking into account functional and chronological aspects. [ABSTRACT FROM AUTHOR]

This paper discusses the issue of the influence of cartographic Terrestrial Laser Scanning (TLS) data conversion into feature-based automatic registration. Automatic registration of data is a multi-stage process, it is based on original software tools and consists of: (1) Conversion of data to the raster form, (2) register of TLS data in pairs in all possible combinations using the SURF (Speeded Up Robust Features) and FAST (Features from Accelerated Segment Test) algorithms, (3) the quality analysis of relative orientation of processed pairs, and (4) the final bundle adjustment. The following two problems, related to the influence of the spherical image, the orthoimage and the Mercator representation of the point cloud, are discussed: The correctness of the automatic tie points detection and distribution and the influence of the TLS position on the completeness of the registration process and the quality assessment. The majority of popular software applications use manually or semi-automatically determined corresponding points. However, the authors propose an original software tool to address the first issue, which automatically detects and matches corresponding points on each TLS raster representation, utilizing different algorithms (SURF and FAST). To address the second task, the authors present a series of analyses: The time of detection of characteristic points, the percentage of incorrectly detected points and adjusted characteristic points, the number of detected control and check points, the orientation accuracy of control and check points, and the distribution of control and check points. Selection of an appropriate method for the TLS point cloud conversion to the raster form and selection of an appropriate algorithm, considerably influence the completeness of the entire process, and the accuracy of data orientation. The results of the performed experiments show that fully automatic registration of the TLS point clouds in the raster forms is possible; however, it is not possible to propose one, universal form of the point cloud, because a priori knowledge concerning the scanner positions is required. If scanner stations are located close to one another in raster images or in spherical images, Mercator projections are recommended. In the case where fragments of the surface are measured under different angles from different distances and heights of the TLS, orthoimages are suggested. [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]

The paper presents analysis of the orientation of terrestrial laser scanning (TLS) data. In the proposed data processing methodology, point clouds are considered as panoramic images enriched by the depth map. Computer vision (CV) algorithms are used for orientation, which are applied for testing the correctness of the detection of tie points and time of computations, and for assessing difficulties in their implementation. The BRISK, FASRT, MSER, SIFT, SURF, ASIFT and CenSurE algorithms are used to search for key-points. The source data are point clouds acquired using a Z+F 5006h terrestrial laser scanner on the ruins of Iłża Castle, Poland. Algorithms allowing combination of the photogrammetric and CV approaches are also presented. [ABSTRACT FROM AUTHOR]

Generation of precise and, at the same time, high resolution architectural documentation, acquired on the basis of terrestrial laser scanning or dense point clouds from digital images is still and open issue, which forms many challenges. Today, close range photogrammetry has great potential for development through the use of low-cost image acquisition tools. Mobile phones, digital camcorders or compact cameras are all sources of data, which potentially allow for the creation of reliable and accurate three-dimensional models of analysed scenes. This paper presents the results of a comparison between these aforementioned sources of image information, acquired by simple and popular cameras, and data acquired from a close range laser scanner. These sets of photos produced several virtual models of small architectural details, supported by Agisoft software. A final rating was conducted using data acquired for the same object using a laser scanner, which was taken as a referential approximation of the three-dimensional shape. [ABSTRACT FROM AUTHOR]

This paper discusses the issue of automation of orthoimage generation based on Terrestrial Laser Scanning (TLS) data and digital images. The following two problems are discussed: automatic generation of projection planes based on TLS data, and automatic orientation of digital images in relation to TLS data. The majority of popular software applications use manual definitions of projection planes. However, the authors propose an original software tool to address the first issue, which defines important planes based on a TLS point cloud utilizing different algorithms (RANdom SAmple Consensus-RANSAC, Hough transform, "region growing"). To address the second task, the authors present a series of algorithms for automated digital image orientation in relation to a point cloud. This is important in cases where scans and images are acquired from different places and at different times. The algorithms utilize Scale Invariant Feature Transform(SIFT) operators in order to find points that correspond in reflectance intensity between coloure images (Red Green Blue--RGB) and orthoimages, based on TLS data. The paper also presents a verification method using SIFT and Speeded-Up Robust Features (SURF) operators. The research results in an original tool and applied Computer Vision(CV) algorithms that improve the process of orthoimage generation. [ABSTRACT FROM AUTHOR]

The presented paper shows the diversity of photogrommetric approaches by introducing a problem of camera interior orientation, data georeferencing. data integration and the issue of automatic object surface modelling. The authors discuss the abovementioned issues on the example of the work carried out at the Faculty of Geodesy and Cartography, Warsaw University of Technology referring to solutions practiced in Computer Vision. This article is an example of introduction of photogrammetry as a discipline open to achievements of close fields of science, which is widely applied in practice [ABSTRACT FROM AUTHOR]

Image network design is a critical factor in image-based 3D shape reconstruction and data processing (especially in the application of combined SfM/MVS methods). This paper aims to present a new approach to designing and planning multi-view imaging networks for dynamic 3D scene reconstruction without preliminary information about object geometry or location. The only constraints are the size of defined measurement volume, the required resolution, and the accuracy of geometric reconstruction. The proposed automatic camera network design method is based on the Monte Carlo algorithm and a set of prediction functions (considering accuracy, density, and completeness of shape reconstruction). This is used to determine the camera positions and orientations and makes it possible to achieve the required completeness of shape, accuracy, and resolution of the final 3D reconstruction. To assess the accuracy and efficiency of the proposed method, tests were carried out on synthetic and real data. For a set of 20 virtual images of rendered spheres, completeness of shape reconstruction was up by 92.3% while maintaining accuracy and resolution at the user-specified level. In the case of the real data, the differences between predictions and evaluations for average density were in the range between 33.8% to 45.0%. [ABSTRACT FROM AUTHOR]

The aim of this article is to present the influence of detector selection for the image-based Terrestrial Laser Scanning (TLS) registration method. The presented results are the extended continuation of investigations presented in the article, 'The Influence of the Cartographic Transformation of TLS Data on the Quality of the Automatic Registration'. In order to obtain the correct results of the TLS registration process, it is necessary to detect and match the correct tie points, which are evenly distributed across the entire area. Commonly, for TLS data registration manually or semi-manually corresponding points are detected. However, when large, complicated cultural heritage objects are investigated, it is sometimes impossible to place marked control points. The only possibility of resolving this problem is the use of image-based TLS data registration. One of the most important factors that influences the quality and ability to use it correctly, is accurate selection. For this purpose, the authors decided to test three blob detectors ASIFT, SURF, CenSurE, and two point detectors FAST and BRISK. The results indicated that selection depends on two factors: if the time required for data processing is not important, the ASIFT algorithm should be used, which allows for full registration, but if not, a combination of other algorithms with results supervision should be considered. [ABSTRACT FROM AUTHOR]

Cultural heritage objects are affected by a wide range of factors causing their deterioration and decay over time such as ground deformations, changes in hydrographic conditions, vibrations or excess of moisture, which can cause scratches and cracks formation in the case of historic buildings. The electromagnetic spectroscopy has been widely used for non-destructive structural health monitoring of concrete structures. However, the limitation of this technology is a lack of geolocalisation in the space for multispectral architectural documentation. The aim of this study is to examine different geolocalisation methods in order to determine the position of the sensor system, which will then allow to georeference the results of measurements performed by this device and apply corrections to the sensor response, which is a crucial element required for further data processing related to the object structure and its features. The classical surveying, terrestrial laser scanning (TLS), and Structure-from-Motion (SfM) photogrammetry methods were used in this investigation at three test sites. The methods were reviewed and investigated. The results indicated that TLS technique should be applied for simple structures and plain textures, while the SfM technique should be used for marble-based and other translucent or semi-translucent structures in order to achieve the highest accuracy for geolocalisation of the proposed sensor system. [ABSTRACT FROM AUTHOR]

This article presents a new approach to the estimation of shift and rotation between two images from different kinds of imaging sensors. The first of the image is an orthophotomap that is created using optical sensors with georeference information. The second one is created utilizing a Synthetic Aperture Radar (SAR) sensor.The proposed solution can be mounted on a flying platform, and, during the flight, the obtained SAR images are compared with the reference optical images, and thus it is possible to calculate the shift and rotation between these two images and then the direct georeferencing error. Since both images have georeference information, it is possible to calculate the navigation correction in cases when the drift of the calculated trajectory is expected. The method can be used in platforms where there is no satellite navigation signal and the trajectory is calculated on the basis of an inertial navigation system, which is characterized by a significant error. The proposed method of estimating the navigation error utilizing Affine Scale-Invariant Feature Transform (ASIFT) and Structure from Motion (SfM) is described, and techniques for improving the quality of SAR imaging using despeckling filters are presented. The methodology was tested and verified using real-life SAR images. Differences between the results obtained for a few selected despeckling methods were compared and commented on. Deep investigation of the nature of the SAR imaging technique and noise creation character allows new algorithms to be developed, which can be implemented on flying platforms to support existing navigation systems in which trajectory error occurs. [ABSTRACT FROM AUTHOR]

All countries around the world are blessed with particularly rich cultural heritage. Nowadays, many researchers are exploring different methods for documentation, management, and sustainability of cultural heritage. The aim of this article is to review the state-of-the-art documentation, management, and sustainability techniques in the field of cultural heritage based on the case study in the Museum of King Jan III's Palace at Wilanów. Various 2D/3D image and range-based methods are discussed demonstrating their applications and drawbacks. The geographical information system (GIS) is presented as a method for management, storage, and maintenance of cultural heritage documentation. [ABSTRACT FROM AUTHOR]

The near-infrared emission in fabricated low-phonon energy, gallo-germanate glass, and double-core optical fiber has been investigated. Broadband amplified spontaneous emission (ASE) was obtained in optical fiber with cores doped with: 1 st - 0.2Er 2 O 3 and 2 nd - 0.5Yb 2 O 3 /0.4Tm 2 O 3 /0.05Ho 2 O 3 as a result of the superposition of emission bands from both cores corresponding to the Er 3+ : 4 I 13/2 → 4 I 15/2 (1 st core) and Tm 3+ : 3 F 4 → 3 H 6 /Ho 3+ : 5 I 7 → 5 I 8 (2 nd core) transitions. The effect of fiber length and pump wavelength on the near-infrared amplified spontaneous emission (ASE) properties has been analyzed for 1 m and 5 m optical fiber. The widest emission bandwidth (355 nm - 3 dB level) was obtained for a 5 m length optical fiber pumped by a 940 nm laser.