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Topographic surface modelling using raster grid datasets by GMT: example of the Kuril–Kamchatka Trench, Pacific Ocean

Abstract

The study area is focused on the Kuril–Kamchatka Trench, North Pacific Ocean. This region is geologically complex, notable for the lithosphere activity, tectonic plates subduction and active volcanism. The submarine geomorphology is complicated through terraces, slopes, seamounts and erosional processes. Understanding geomorphic features of such a region requires precise modelling and effective visualization of the high-resolution data sets. Therefore, current research presents a Generic Mapping Tools (GMT) based algorithm proposing a solution for effective data processing and precise mapping: iterative module-based scripting for the automated digitizing and modelling. Methodology consists of the following steps: topographic mapping of the raster grids, marine gravity and geoid; semi-automatic digitizing of the orthogonal cross-section profiles; modelling geomorphic trends of the gradient slopes; computing raster surfaces from the xyz data sets by modules nearneighbor and XYZ2grd. Several types of the cartographic projections were used: oblique Mercator, Mercator cylindrical, conic equal-area Albers, conic equidistant. The cross-section geomorphic profiles in a perpendicular direction across the two selected segments of the trench were automatically digitized. Developed algorithm of the semi-automated digitizing of the profiles enabled to visualize gradients of the slope steepness of the trench. The data were then modelled to show gradient variations in its two segments. The results of the comparative geomorphic analysis of northern and southern transects revealed variations in different parts of the trench. Presented research provided more quantitative insights into the structure and settings of the submarine landforms of the hadal trench that still remains a question for the marine geology. The research demonstrated the effectiveness of the GMT: a variety of modules, approaches and tools that can be used to produce high-quality mapping and graphics. The GMT listings are provided for repeatability.

Open access
A method for local approximation of a planar deformation field

Abstract

We present a method of approximation of a deformation field based on the local affine transformations constructed based on n nearest neighbors with respect to points of adopted grid. The local affine transformations are weighted by means of inverse distance squared between each grid point and observed points (nearest neighbors). This work uses a deformation gradient, although it is possible to use a displacement gradient instead – the two approaches are equivalent. To decompose the deformation gradient into components related to rigid motions (rotations, translations are excluded from the deformation gradient through differentiation process) and deformations, we used a polar decomposition and decomposition into a sum of symmetric and an anti-symmetric matrices (tensors). We discuss the results from both decompositions. Calibration of a local affine transformations model (i.e., number of nearest neighbors) is performed on observed points and is carried out in a cross-validation procedure. Verification of the method was conducted on simulated data-grids subjected to known (functionally generated) deformations, hence, known in every point of a study area.

Open access
GPR surveying method as a tool for geodetic verification of GESUT database of utilities in the light of BSI PAS128

Abstract

Intensified investment processes in construction have resulted in increased interest in the methods of efficient detection, verification and location of underground utility networks. In addition to the well-known pipe and cable locating equipment, which has increased its efficiency and reliability through the development of technologies, GPRs are becoming more and more popular.

This publication presents the results of the experimental research carried out with the use of GPRs manufactured by two different companies as well as the results of the verification of underground utilities in real conditions. The GPRs have worked in the mode of the real-time location of their own position using the GNSS system or robotic total stations.

The GPR (Ground Penetrating Radar) surveys performed on a test field, consisting of 9 pipes with a known position, were aimed at assessing the accuracy of their identification on echograms. The utility line location errors were determined using three different combinations between the GPR and the locating instrument. It allowed the evaluation of the possibility of using these solutions for detection, verification and location of underground utility networks in the light of the Polish legal regulations and the British specification PAS 128.

The verification in real conditions was carried out in a typical urban space, characterised by an intense occurrence of underground utilities, that is, sewage systems, gas pipelines and power cables. It was based on the GESUT database captured from the county geodetic and cartographic documentation centre. The results of the visual analysis of the materials captured with the help of two measurement systems were described in detail, however, the verification was carried out only for one set of data. The authors have presented the procedure of processing echograms and detecting the location of pipeline axes based on their vectorisation. The authors of this research paper have performed a numerical analysis of the compliance of the profiles of utility lines with the information from the base map for two variants of the GPR data integration with the coordinates. The authors of this research paper have also presented an alternative concept of capturing the profile of a utility line in the field based on the processing of GPR data in 3D – the so-called C-scan. The conclusions summarise the possible factors affecting the surveying results and the methods of eliminating sources of errors, both for the GPR and geodetic data.

Open access
High-energy seismic events in Legnica–Głogów Copper District in light of ASG-EUPOS data

Abstract

Seismic events in the area of Poland are related mostly to copper and coal mining, and they are regarded as the most dangerous natural hazard. Although development of geomechanical modelling as the development of geophysical methods determining seismic hazard are evident, low predictability of the time-effect relationship still remains. Geomechanical models as geophysical data analysis highlight the interaction between parts of rock mass or allow to reconstruct the way of rock mass destruction and to understand the processes that take place in the high-energy tremors.

However, the association of larger mining tremors with pre-existing geological features has been reported by many investigators; in geomechanical practice, investigations of rock mass condition concentrate on this problem in the local scale. Therefore, the problem of relations between high-energy seismic events in Legnica–Głogów Copper District (LGCD) and regional scale deformations of terrain surface resulting from possible tectonic activity is discussed in this paper. The GNSS data evaluated from the observations of ASG-EUPOS (Active Geodetic Network – EUPOS) stations in the area of LGCD and in the adjacent areas is analysed in this study. Temporal variation of distances between the stations and evaluated on that base so called apparent strain was combined with the occurrence of high-energy tremors. Consequently, after the examination and analysis of occurrences of mining tremors, it is found that high-energy seismic events and periods of strain accumulation evaluated from GPS/GNSS data have temporal relations. Although the seismic events were triggered by mining, nearly all the events with energy E > 108 J occurred in the periods when the analysed stations’ positions demonstrated a decrease in the baseline length.

Open access
Transformation of 3D geospatial data into CityGML – a case of Prague

Abstract

The 3D geoinformation is becoming important for cities and their policies. The cities are therefore exploring the possibilities of 3D virtual city models for more efficient decision making. To maximize the economic benefit of such data, the cities can provide their 3D geospatial data for further usage, and so, new applications can be created. The paper defines a way how the freely available 3D geospatial data of Prague can be transformed from the proprietary data format into the open data model. The 3D geospatial data about the buildings, bridges and digital terrain model were transformed from the 3D shapefile into the CityGML. This is an application independent information model and exchange format. This will allow for the wider use of the 3D city model by different groups of users. The generated CityGML files were further imported into the spatial database with appropriate database CityGML-based scheme. It enables more efficient management and querying of CityGML data. To enable the wider audience to explore the 3D city model, the visualization in the web environment was also explored. The paper also presents the way how the attributes from the external data sources can be connected to the 3D objects in the web environment.

Open access
The accuracy investigation of point coordinates’ determination using a fixed basis for high-precision geodesy binding

Abstract

Modern scanners can perform terrestrial topographic survey with resolution of 1 cm and accuracy of 2 mm in just a few minute‘s time, from the distance of up to 100 meters. However, for surface topographical surveying of large territories or complex industrial objects, it is necessary to conduct geodetic traverses and perform their binding to the points of the geodesic basis. One method of coordinate transferring during surveying is by using the method of inverse linear-angular intersection, which involves the measuring of the respective sides S 1, S 2 and the β angle between them. This method is more precise than the classical one, which usually contains centring and reduction errors. The linear-angular intersection method can also be used for many applications in engineering geodesy, for laying geodetic traverses, and for binding to the wall based points of ground-surveying.

Open access
Determining of correlation relationship between roll, pitch, and yaw for UAVs

Abstract

Currently, UAVs are intensively being introduced into topographic-photogrammetric production for topographic digital aerial photography and laser scanning. These technologies have a number of advantages: they don’t require specially prepared platforms and launchers, they are relatively inexpensive unlike large aircrafts, and they are safe. However, there are still many unsolved problems for ultralight UAVs, especially when the aerial photography is made. As you know, the requirements for the implementation of the aerial survey process are quite stringent, first of all, for horizontal flight: the angles of inclination must be within 3–5 degrees, since exceeding these tolerances significantly affects the accuracy for determining the spatial coordinates of objects. Therefore, there was an idea to conduct researches of dependences between the pitch α, roll ω and yaw κ. For this purpose, 100 images obtained from aircraft-type UAV ‘Arrow’ developed and created by specialists from Lviv Polytechnic National University and ‘Abris’ were used. As a result of the study, the multiple correlation coefficient and the parameters of the linear regression equation for the angular elements of the exterior orientation of digital images were calculated. In addition, statistical quality evaluations for the obtained regression model were carried out. Analysis of the received data allows to assert that angular elements of exterior orientation are correlated with each other. Therefore, in the further imaging materials, processing it becomes possible to make compensation of this fact and to improve calculation accuracy of spatial coordinates of points.

Open access
Urban area change visualization and analysis using high density spatial data from time series aerial images

Abstract

Urban changes occur as a result of new constructions or destructions of buildings, extensions, excavation works and earth fill arising from urbanization or disasters. The fast and efficient detection of urban changes enables us to update geo-databases and allows effective planning and disaster management. This study concerns the visualization and analysis of urban changes using multi-period point clouds from aerial images. The urban changes in the city centre of the Konya Metropolitan area within arbitrary periods between the years 1951, 1975, 1998 and 2010 were estimated after comparing the point clouds by using the iterative closest point (ICP) algorithm. The changes were detected with the point-to-surface distances between the point clouds. The degrees of the changes were expressed with the RMSEs of these point-to-surface distances. In addition, the change size and proportion during the historical periods were analysed. The proposed multi-period change visualization and analysis method ensures strict management against unauthorized building or excavation and more operative urban planning.

Open access
Geodetic monitoring of earth-filled flood embankment subjected to variable loads

Abstract

The article presents an example of supplementing geotechnical monitoring with geodetic observations. The experimental flood embankment built within the ISMOP project (Information Technology System of Levee Monitoring) was subjected to continuous monitoring based on built-in measuring sensors. The results of geodetic monitoring used for observation of earth-filled flood embankment subjected to external loads are presented in the paper. The tests were carried out on an experimental food embankment forming a closed artificial water reservoir. The observations were carried out for two purposes. The first was long-term monitoring, which was aimed to determine the behaviour of the newly built embankment. The second purpose was to check the reaction of the levee to the simulated flood wave, caused by filling and draining the reservoir. In order to monitor the displacements of the earth-filled embankment, it was necessary to develop the proper methodology. For the needs of research works, an appropriate network of 5 reference points and 48 survey markers has been designed and established. The periodic measurements were carried out using precise robotic total station. The stability of the reference frame was each time checked and displacements of survey markers were determined based on it. The final results allow to reveal the reaction of levee to external loads. The displacement values were referred to the course of the filling and draining experiment to indicate the relationship between them. In the field of long-term monitoring the results clearly imply the dominance of displacements outside the reservoir for points located on the embankment, in contrast to points on the crest and foreground, which do not show significant movements. On the other hand, in the field of testing the embankment reaction to the flood wave, obtaining reliable results was possible thanks to high-accuracy geodetic measurements. Small displacement values, often at the level of their determination errors, were averaged for groups of points with the same height of foundation. A sizable number of points allows to perceive some tendencies and the relation between embankment soaking, hence its movement directions can be noticed. During periods when the levee was still saturated with water, slight movements outside the reservoir were revealed. On the other hand, the following period of drying caused movement in the opposite direction.

Open access
Headframe modelling accuracy for finite element method analysis purposes

Abstract

Nowadays, the growing popularity of terrestrial laser scanners (TLS) allows to obtain a point cloud of many industrial objects along with classic surveying. However, the quality and model’s accuracy in comparison to a real shape seem to be a question, that must be further researched. It is crucial especially for Finite Element Method (FEM) analysis, which, being a part of technical design, estimate the values of construction’s dislocation and deformation. The article describes objects such as headgear with steel support and 4-post headframe with steel sheers. Both supports and sheers were modelled basing on point clouds. All the models were compared to the point cloud. The differences in models’ shape were calculated and the maximal values were determined. The results’ usefulness in FEM analysis was described.

Open access