The landscape shaped by the energy industry is rich in various slender structures, such as smokestacks, cooling towers, and others. It is thus becoming increasingly important to effectively monitor the geometrical condition of all types of such structures. Slender structures are deformed elastically under loads due to wind. A proper analysis of the changes and deformations of such structures requires a continuous ground-based measurement system which allows the movement of the structure to be measured in two horizontal directions, from a significant distance and with a possibly reduced number of stations. For this purpose, two methods were implemented: a linear terrestrial laser scanning method (TLS) and an optical, direct distance measurement method—tachymetry (TCH). The least squares method was used to fit rings on various levels of the structure and then the centers of the rings were identified. The comparison of the identified ring centers enabled the axis of the structure to be measured for deviation in two perpendicular directions. The methods were verified on actual structures: a smokestack 110 m in height, a cooling tower 60 m in height, and a wind turbine with the rotor axis at 149 m. The measurement results were compared with respect to the measurement time and the obtained accuracies at which the point locations were identified on the structure. The proposed methods are an effective tool for monitoring the condition of slender objects both during their operating life and after it. Regular monitoring of the geometric condition of slender structures in the energy industry limits the risk of major or catastrophic events, and as a result allows the safe and uninterrupted delivery of electric energy to clients.
The article presents geomorphological analysis results for two outwash fans (sandurs), Elveflya and Nottingham, in the marginal zone of the Werenskiold Glacier in the south-west part of the Spitsbergen. The main goal of this study was to reconstruct the morphological evolution of these landforms and to identify the permafrost zone under their surface. For this purpose, age data of fossils were compiled and compared with newly exposed and dated fossil tundra in the layer glaciotectonically deformed by the forming glacier end moraine. Using this method, a time frame was identified for the glacier advance and for the simultaneous formation of the outwash plains. It was concluded that the Elveflya surface has been built-up with deposits since the Little Ice Age. Sediment deposition ended in the late 1960s, due to hydrographic changes and the redirection of all proglacial waters towards the Nottingham bay. A photointerpretation analysis based on two orthophotomaps and LANDSAT scenes allowed the identification of five microfans in Elveflya, of which two youngest fans have a twice shorter range than the other three. The sixth microfan is currently shaped by deposits washed from the slope of the end moraine. An additional focus was placed on a currently active sandur, which fills the Nottingham bay, in order to identify its growth rate. The average growth rate of this surface increased from 5700 m2·year−1 over the period of 1985–2000 to 24,900 m2·year−1 over the period of 2010–2017. Electromagnetic measurements carried out on the surfaces of the sandurs demonstrated that the electrical resistivity of the ground is high in the apex of the Elveflya fan (ρ ≥ 1 kΩ.m) and low in its toe (typically ρ < 200 Ω.m), as in the case of the Nottingham fan ground. In the interpretation advanced here, permafrost developed in the proximal part of the Elveflya sandur, which continues to be supplied by fresh groundwaters flowing from the glacier direction. Low electrical resistivity of the ground in the distal part of the outwash fan suggests the absence of ground ice in this zone, which is subjected to the intrusion of salty and comparatively warm seawater, reaching approximately 1 km inland under the surface of the low-elevated marine terrace. The identified zones additionally display different tendencies for vertical movements of the terrain surface, as identified with the Small Baseline Subset (SBAS) method. The proximal part of the Elveflya outwash fan is relatively stable, while its distal part lowers in the summer period by a maximum of 5 cm. The resulting morphological changes include linear cracks having lengths up to 580 m and an arc line consistent with the coastline.
12 June 2018 in IOP Conference Series: Materials Science and Engineering
Safe operation of thin-walled objects requires a regular monitoring of their technical condition. Geodetic measurements performed with a terrestrial laser scanning allow to determine the geometrical shape of the tested object with very high detail. Thermovision, as an auxiliary method, allows identification of places particularly exposed to changes in geometry caused by thermal influences. This paper presents a combination of both methods to analyse the geometry of reinforced cooling tower with a height of about 170 m. Laser scanning was performed from 11 stations arranged around the cooling tower, and the acquired point clouds were combined and unified in terms of density. Comparing the actual shape of the shell with the theoretical model, the values of geometrical imperfections were calculated. Thermograms were made by means of the thermovision camera, with particular emphasis on the lower part of the shell. The analysis of the imperfections' distribution and the location of the largest temperature differences allowed to identify the most threatened places on the cooling tower shell.
Wrocław is a major city located in the southwestern part of Poland in an aseismic tectonic fault zone. Slow, long-term, vertical displacements have been observed there from the 1930s based on the levelling network measurements with the use of a precise levelling method. Due to the high cost of classic surveys, these were performed at intervals of several decades and the most recent measurement of ground surface displacement was performed in 1999. The main aim of this study is to determine the ground surface displacements on the area of Wrocław in the 1995–2019 period, the spatio-temporal analysis of deformations and the identification of the potential factors causing these deformations. To determine the ground movements, an advanced PSI technique and data from ERS-2, Envisat, and Sentinel-1 sensors were used. Application of SAR technology for the first time in this area, provided new knowledge about the process of deformation in short time intervals over the entire area of the city. The results verify the hypothesis on the linearity of displacements obtained from historical geodetic observations. The obtained results show that the displacements, which continue to occur in the area of Wrocław have a cyclic character with 4–5 year long period of subsidence and 2–3 year long periods of stabilization or uplift. The displacement trends indicate that the area of the city gradually subsides in relation to the reference area located on the Fore-Sudetic Block.
Werenskiold Glacier in the Isle of Spitsbergen is one of the polygons on which evaluation of the rate of glacier recession is performed. Location of the glacier front is precisely presented in the specialist literature since the mid. 30. of 20th century. Article presents results of studies about changes in the position of Werenskiold Glacier based on selected archival data and own research conducted in 2012-2013. The initial location of the glacier front was described by the topographical map in the scale 1:5000 elaborated in the year 1961 on the basis of data from the years 1957-1959 by the Polish Army Topographic Service. Moreover, as comparative data on location of glacier front in the later years there were applied results of photogrammetrical images from the year 1973 and a orthophotomap from 1990. These data together with the author's GPS measurements were transformed into the uniform coordinate system. Thus, prepared data made it possible to evaluate the rate of recession of Werenskiold Glacier front in the three epochs from the years 1957-2013. It was found that during the 56 years the glacier front was moved by ca. 1200 m, which gives the mean recession value of 25 m/year as well as the mean yearly loss of the glacier surface of the order of 5 ha.
Dynamic climate changes are particularly apparent in polar regions. Glaciers are retreatng towards the land at a very fast pace. This study demonstrates the application of the feature tracking method in the analysis of ice flow velocity in the region of the Hornsund fiord, southern Spitsbergen, in the years 2018–2022. The calculations were based on the Geogrid and autoRIFT environments and on the Sentinel 1 images. The study also employed external data, such as a numerical terrain model and reference velocity values. The input data, e.g., the chip size and the search limit, were prepared accounting for the specific character of the investigated area. The velocities were calculated for nine biggest glaciers which terminated in the fiord. The accuracy of the results was identified by calculating the median absolute deviation (MAD) of the obtained displacement velocity values from the reference value for areas identified as stable. The study also attempted a causal analysis of the influence of weather factors on the dynamics of ice mass displacement. A systematic year-to-year decrease of the velocity was observed for the entire fiord. In the case of several glaciers, changes related to the ablation season (summer) are also clearly visible. The research results are promising and fill a research gap related to the absence of permanent monitoring and analysis of the dynamics of ice flow in polar regions. It is the first complex and precise study of glacier surface velocity changes, performed on the basis of satellite radar images for the entire Hornsund fiord.