The paper contains a survey of mobile scanning systems for measuring the railway clearance gauge. The research was completed as part of the project carried out for the PKP (PKP Polish Railway Lines S.A., Warsaw, Poland) in 2011–2013. The authors conducted experiments, including a search for the latest solutions relating to mobile measurement systems that meet the basic requirement. At the very least, these solutions needed to be accurate and have the ability for quick retrieval of data. In the paper, specifications and the characteristics of the component devices of the scanning systems are described. Based on experiments, the authors did some examination of the selected mobile systems to be applied for measuring the clearance gauge. The Riegl (VMX-250) and Z+F (Zoller + Fröhlich) Solution were tested. Additional test measurements were carried out within a 30-kilometer section of the Warsaw-Kraków route. These measurements were designed so as to provide various elements of the railway infrastructure, the track geometry and the installed geodetic control network. This ultimately made it possible to reduce the time for the preparation of geodetic reference measurements for the testing of the accuracy of the selected systems. Reference measurements included the use of the polar method to select profiles perpendicular to the axis of the track. In addition, the coordinates selected were well defined as measuring points of the objects of the infrastructure of the clearance gauge. All of the tested systems meet the accuracy requirements initially established (within the range of 2 cm as required by the PKP). The tested systems have shown their advantages and disadvantages.

<p><strong>Abstract.</strong> Nowadays UAV photogrammetry becomes a common method for mapping and surveying. At the same time due to the increasing range of work carried out with UAV, the importance of final product accuracy increases. However to obtain survey-grade accuracy it is necessary to perform bundle adjustment processes that could be affected by multiple factors like unstable camera calibration, correlation between interior and exterior orientation and insufficient georeference information. One of the aims of the project was to prepare the terrestrial test field, which helps to obtain optimal decorrelation and allows to objectively assess the accuracy of the bundle adjustment in UAV application. During the project, two multi-variant flights over the test field were conducted. The flights were performed with a fixed-wing airframe equipped with PPK receiver on-board. Based on the conducted flights, many data sets have been prepared, which differ as follows: types of cameras, GSD, flight direction and georeferenced method.</p>

Abstract:The methods used for image contrast enhancement in the wavelet domain have been previously documented. The essence of these methods lies in the manipulation of the image during the reconstruction process, by changing the relationship between the components that require transformation. This paper proposes a new variant based on using undecimated wavelet transform and adapting the Gaussian function for scaling the coefficients of detail wavelet components, so that the role of low coefficients in the reconstructed image is greater. The enhanced image is then created by combining the new components. Applying the Haar wavelet minimises the effects of the relationship disturbance between components, and creates a small buffer around the edge. The proposed method was tested using six images at different scales, collected with handheld photo cameras, and aerial and satellite optical sensors. The results of the tests indicate that the method can achieve comparable, or even better enhancement effects for weak edges, than the well-known unsharp masking and Retinex methods. The proposed method can be applied in order to improve the visual interpretation of remote sensing images taken by various sensors at different scales.

Recently, the term smartphone photogrammetry gained popularity. This suggests that photogrammetry may become a simple measurement tool by virtually every smartphone user. The research was undertaken to clarify whether it is appropriate to use the Structure from Motion—Multi Stereo View (SfM-MVS) procedure with self-calibration as it is done in Uncrewed Aerial Vehicle photogrammetry. First, the geometric stability of smartphone cameras was tested. Fourteen smartphones were calibrated on the checkerboard test field. The process was repeated multiple times. These observations were found: (1) most smartphone cameras have lower stability of the internal orientation parameters than a Digital Single-Lens Reflex (DSLR) camera, and (2) the principal distance and position of the principal point are constantly changing. Then, based on images from two selected smartphones, 3D models of a small sculpture were developed. The SfM-MVS method was used, with self-calibration and pre-calibration variants. By comparing the resultant models with the reference DSLR-created model it was shown that introducing calibration obtained in the test field instead of self-calibration improves the geometry of 3D models. In particular, deformations of local concavities and convexities decreased. In conclusion, there is real potential in smartphone photogrammetry, but it also has its limits.

This paper details the development of a camera calibration method purpose-built for use in photogrammetric survey production. The calibration test field was established in a hangar, where marker coordinates were measured using a high-precision survey methodology guaranteeing very high accuracy. An analytical model for bundle adjustment was developed that does not directly use the coordinates of field calibration markers but integrates bundle adjustment and survey observations into a single process. This solution, as well as a classical calibration method, were implemented in a custom software, for which the C++ source code repository is provided. The method was tested using three industrial cameras. The comparison was drawn towards a baseline method, OpenCV implementation. The results point to the advantages of using the proposed approach utilizing extended bundle adjustment.

ABSTRACT:The detection of orthoimage mosaicking seamlines by means of wavelet transform was examined. Radiometric alignment was omitted, giving priority to the issue of seamlines which bypass locations where there is a parallax between orthoimages. The importance of this issue is particularly relevant for images with very high resolution. In order to create a barrier image between orthoimages, the redundant wavelet transform variant known as MODWT-MRA was used. While more computationally complex than the frequently used DWT, it enables very good multiresolution edge detection. An IT prototype was developed on the basis of the described concept, and several cases of seamline detection were tested on the basis of data with a resolution of 10 cm to 1 m. The correct seamline location was obtained for each test case. This result opens the door to future expansion of the radiometric alignment method, which is also based on wavelets.

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Abstract. Measuring of railway structure clearances is a very practical issue, and the operation itself is performed all over the world using various measuring systems. The measurement is aimed chiefly at determining the limits of space that no structure (e.g. a building) located close to the railway track may cross. The paper demonstrates flaws and advantages of particular systems and provides a technological summary of measuring equipment utilized in them. In those systems the measurement of structures is referred to the global system of coordinates, and later, following the detection of rail heads, a transformation to the rail axis arrangement takes place. The preliminary analysis leads to a conclusion that the accuracy of rail clearance measurement is higher in the case of specialized systems as compared to universal ones. On the basis of experience drawn from literature and earlier tests, a decision has been made to proceed with the construction of a rail clearance measurement system in Poland, at the University of Science and Technology in Cracow. This paper presents a research on the prototype of the rail clearance measurement system constructed at the University. The heart of the system involves laser scanners installed on a flatcar and digital cameras. The base of the system includes scanners, which capture data in a continuous way, and photogrammetric cameras, which yield digital images. The cloud of points obtained from a laser scanning is colorized, which causes that such information can replace a classical texture model.