The second issue, No. 2
Sławomir Tulski 
, Kazimierz Bęcek
Two methods to mitigate insar-based dems vegetation impenetrability bias
Corresponding author
DOI: http://dx.doi.org/10.15576/GLL/2021.2.7
Digital elevation models (DEM), including the Shuttle Radar Topography Mission (SRTM), are used in many branches of geoscience as an ultimate dataset representing our planet’s surface, making it possible to investigate processes that are shaping our world. The SRTM model exhibits elevation bias or systematic error over forests and vegetated areas due to the microwaves’ peculiar properties that penetrate the vegetation layer to a certain depth. Numerous investigations identifi ed that the penetration depth depends on the forest density and height. In this contribution, two methods are proposed to remove the impact of the vegetation impenetrability eff ect. The first method is founded on the multiple regression of two forest characteristics, namely forest height and forest density. The second method uses a lookup table approach. The lookup table and the multiple regression explanatory variables are taken from the freely available datasets, including the forest density data (MODIS_VCF) and global tree height map (GTHM). An important role in this research is played by the Ice, Clouds, and Land Elevation Satellite (ICESat) data. The accuracy tests indicate that the fi rst method eliminates approximately 68% of the elevation bias, while the second method appears to be more effective, leading to almost complete removal of the vegetation bias from the SRTM data. The methods are fi ne-tuned to the local coniferous forests in Poland. Additional studies are required to fi netune the methods for the leaf-off state of deciduous forests. However, a new set of parameters for both methods can be quickly developed for diff erent locations and forest types. Both methods’ functionality and eff ectiveness can be improved once more accurate forest tree height and vegetation density data become available. These methods are universal in mitigating the vegetation bias from the Synthetic Aperture Radar Interferometry (InSAR) derived model and photogrammetric models.
Keywords: SRTM • vegetation bias • impenetrability • ICESat • GTHM
Tadeusz Gargula
Point position accuracy in a vector gnss network and the way it is linked to reference stations
Corresponding author
DOI: http://dx.doi.org/10.15576/GLL/2021.2.23
The aim of this study is to assess the impact of the location (distribution) of reference points (reference stations of the ASG-EUPOS system) on the accuracy of the fi nal determination of the local measurement grid points. The research was carried out in terms of the possibility of using the static GNSS method to determine displacements, both relative (vector lengths) and absolute (coordinates in the spatial system). A mathematical record of the computational process (functional model and stochastic model) was presented, on the basis of which the test vector network was adjusted (indirect method) and the accuracy assessment aft er the adjustment was performed. The subject of the numerical tests were the actual measurement results of a part of the geodetic network (GNSS vectors) established in the mining area (the results of one of the periodic measurement cycles were used). Numerical analyses take into account several diff erent variants of establishing the network: depending on the location (direction east–west, north–south) and the number of ASG-EUPOS stations used. The following parameters (relating to the designated positions) were adopted as comparative criteria: coordinate deviation (in the Cartesian geocentric system) from the reference values, spatial length deviation between the designated points from its reference value, mean coordinate errors, error in the position of a point in three-dimensional space, length mean error as a function of adjusted observations (using the law of transfer of errors of mean correlated quantities). Particular attention was paid to the discrepancy between the adjustment results for diff erent systems of reference to the ASG-EUPOS stations. On the basis of the performed calculation tests and the performed comparative analyses, conclusions were compiled that may be helpful in planning periodic measurements for the purpose of determining land displacements.
Keywords: GNSS vector network • establishing a geodetic control network • ASG-EUPOS reference station • rigorous adjustment • determining terrain displacements
Izabela Piech , Artur Borgiasz
The use of UAV data for photogrammetric documentation
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DOI: http://dx.doi.org/10.15576/GLL/2021.2.39
Photogrammetry is a rapidly developing fi eld of science, using new technologies such as unmanned aerial vehicles (UAVs) and digital cameras. Currently, unmanned aerial vehicles are not only used for amateur or professional commemorative aerial photos, but also have much more specialized applications. New technologies allow for faster development of numerous fields of science and provide better results with less work and resources. Unmanned aerial vehicles are used for photogrammetric raids, which produce photogrammetric images of terrain surface or buildings. This allows the generation of orthophotos, and even three-dimensional terrain models, enabling further analysis of a research area. The aim of the study was to make an orthophotomap of the cemetery in the Sułoszowa municipality on the basis of data obtained during a drone raid and to compare it with the existing orthophotomap. The goal was planned to be achieved through the following steps: importing images to Agisoft PhotoScan and georeferencing them to ensure metricity of subsequent studies, generating an orthophotomap and a cloud of points mapping the studied area, compilating and comparing the resulting numerical data, as well as graphic data.
Keywords: UAV • photogrammetric documentation • orthophotomap
Paulina Bidzińska
Geomorphometry of the physical and geographical microregion of the Polkowice Hills
Corresponding author
DOI: http://dx.doi.org/10.15576/GLL/2021.2.59
In this paper, a morphometric analysis of the terrain sculpture was carried out along with the editing of a geomorphometric map of the physical and geographical microregion of the Polkowickie Hills, which so far was not present in the literature for the studied area. The analysis was performed using the GIS program (ESRI ArcMap), which is based on a digital elevation model (LiDAR - DEM). Following primary topographic parameters were selected through digital elevation model processing: aspect, slope, planar curvature, vertical curvature and local height diff erece, which provide exact information about the variability of the topography and its surface morphological processes. The obtained results of primary parameters allowed for the classifi cation of relief forms in the studied area using the unsupervised ISODATA classifi cation method. The fi nal stage consisted of editing a geomorphometric map of the Polkowickie Hills microregion and a presentation of the distribution of morphometric classes with the height division of boundaries of the obtained geomorphometric separations.
The results of the calculations and analyses allowed for the separation of various areas in the Polkowice Hills, and giving them their own names by the author. The choice of the unsupervised classifi cation method and the independent defi nition of the number of classes gave positive results of terrain clustering of the studied area. The compliance of the results of the selected classifi cation method with the actual topography (of which the author has extensive fi eld and observational knowledge) confi rms the selection of appropriate geomorphometric indicators and the unsupervised classifi cation method, which in the examined case turned out to be computationally eff ective.
Keywords: geomorphometry • geomorphometric indicators • unsupervised classifi cation • Polkowice Hills • geomorphometric map
Zbigniew Muszyński , Paulina Kujawa
Vertical displacement measurements as an important aspect of education of geodetic surveyors
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DOI: http://dx.doi.org/10.15576/GLL/2021.2.71
The rapid development of industry, the automation of production, processing, and mining processes increasingly put more demands on the scope and accuracy of geodetic surveying. Obtaining precise data on the spatial location of objects involved in the production process is indispensable for the effi cient management of that process. Registered changes in the geometry of objects may indicate potential threats that may adversely aff ect the safe operation of the given object. One of the most diffi cult tasks in engineering surveying is the control of displacements and deformations of building objects and their surroundings. Th is issue is very broad and concerns most industrial facilities, including opencast mines, landslide areas, cooling towers, water dams, as well as securing deep excavations in compact urban development, verticality control of industrial chimneys and wind farms. Each object has its own specifi c features and requires an individual approach in the fi eld of measuring network design, the selection of an appropriate measurement technique, and systematic geodetic monitoring of displacements. The key aspect is the professional experience of the surveyor – the geodesist who is managing this type of work. Already at the stage of educating future engineers, it is important not only to provide them with appropriate theoretical knowledge, but also to enable them to acquire practical skills. For this reason, science camps have been organized since 2013 as part of the process of educating geodesy and cartography students at the Wrocław University of Science and Technology. The thematic scope of the camps includes the measurement of displacements of a unique engineering structure over 50 meters high, which is the fi gure of Christ the King of the Universe, located in Świebodzin. Students gain professional experience using the latest measuring instruments: digital precision levels, motorized electronic total stations, GNSS satellite receivers, and laser scanners. The students, who face real-life surveying challenges, gain valuable professional experiences that improve their qualifi cations and better prepare them for their future work. The article presents science camps as one of the additional forms of educating surveyors. The scope of work performed during the science camp is presented, and the basic measurement techniques are described. Particular attention was paid to the empirical assessment of the accuracy of the results of measurements of vertical displacements performed by students using the precision levelling method. For the measurement data collected over a period of 8 years, the mean levelling errors were calculated on the basis of the analysis of the levelling sections and polygons. The obtained accuracy meets the requirements for measurements performed in order to determine vertical displacements.
Keywords: vertical displacements • precise levelling • empirical accuracy assessment • science camps
Małgorzata Radło-Kulisiewicz
Review of DTM derivatives most used in digital soil mapping
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DOI: http://dx.doi.org/10.15576/GLL/2021.2.87
Digital Soil Mapping (DSM) is a subdiscipline of pedology, where soil cover is modelled through use of spatial – temporal relations between environmental covariates and soil. The process of quantitative terrain description used in DSM is called terrain parametrization, where terrain attributes (morphometric factors, Digital Terrain Model derivatives) are the most used predicators. Terrain parameterisation was used as a tool in the hydrological survey workshop long before computers had been in use. With the development of digitisation, it also began to be used to determine selected soil attributes, which was greatly facilitated by GIS applications. A signifi – cant breakthrough in the importance of terrain attributes in the creation of soil maps and models took place with the formalisation of rules for digital soil mapping. Literature describes over 50 indices, although only a few of them are commonly applied. This applies to single soil attributes as well as more advanced implementations in more sophisticated models such as artifi cial intelligence algorithms. The aim of the following article is to present the main components of DSM and to describe characteristics of the most commonly derivatives of DTM applied there, also refers to several examples of the use of terrain parameters in the context of DSM in terms of the resolution of the elevation model used.
Keywords: digital soil mapping • DTM • terrain attributes • GIS
Bogusława Kwoczyńska
Analysis of land use changes in the Tri-City metropolitan area based on the multi-temporal classification of landsat and rapideye imagery
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DOI: http://dx.doi.org/10.15576/GLL/2021.2.101
The aim of the study was to diagnose the main trends of land cover changes around urban agglomerations over the last twenty years (1997–2016) on the example of Tri-City, and to present them statistically and graphically in the form of compilation of numerical maps. The research was performed on the basis of remotely sensed data: LANDSAT 5 TM satellite imagery from 1997 and RapidEye from two records (2011, 2016).
The metropolises of Gdańsk, Gdynia and Sopot, constituting the core of metropolitan area (MA), and municipalities belonging to the Tri-City MA located in its vicinity were selected for detailed analyses – the inner zone of 2 communes and the outer zone, also of 2 communes (MA outskirts). In the selected metropolitan area, communes with good and poor natural conditions for agricultural production were studied.
The analyses were performed on processed images (colour compositions), which were subjected to supervised classifi cation with the maximum likelihood technique. The quality control of supervised classifi cation showed an accuracy of 87.2% for LANDSAT 5 TM scene analyses and 93.8% for RapidEye imagery. The Kappa coeffi cient for the discussed classifi cation was, respectively: 0.85 (LANDSATTM) and 0.93 (RapidEye).
The conducted analyses showed that in the communes there were changes in the way of using arable land and grassland. The greatest changes took place in communes with a low Agricultural Production Space Valuation Ratio (APSVR). Grassland, and to a lesser extent areas with scattered development, replaced arable land. In Gdańsk, Sopot and Gdynia, belonging to the Tri-City, the greatest changes over 20 years took place in arable land, which altogether diminished by 17%, and forest land (13% in total). All this to the benefi t of grassland (increase by 23%) and built-up areas (10% in total in all cities).
Keywords: land use • satellite imagery • metropolitan area
Izabela Piech , Damian Kowalski
3D visualization of interiors – the case of “U Jaksy” gallery
Corresponding author
DOI: http://dx.doi.org/10.15576/GLL/2021.2.121
Many generations have tried to represent the surrounding space, oft en striving to do so in the most accurate way, precisely refl ecting details and shapes. An important step towards the faithful representation of reality was the creation of photography. Over time, the two-dimensional spatial imaging became insuffi cient, forcing the creator to choose the appropriate perspective and a comprehensive, holistic view of the object. It became possible to recreate the third dimension using two-dimensional photographs, e.g. by creating a stereogram, a panorama, or developing a 3D model. Techniques related to 3D modelling have become a very important element of contemporary photogrammetry, and they allow for an interesting, eff ective, and metrically accurate manner of depicting reality. 3D models can be used for the inventory of objects, for their reconstruction, and for their presentation. Today, there is a great need to represent the world around us in the digital space, starting from selling products whose 3D models make it possible to see that product from every side, to the creation of three-dimensional maps with street views, such as Google street view, to creating virtual city and museum walks. The products of 3D graphics are not only used for visual eff ects. The models’ metric accuracy also enables numerous engineering applications. Among other things, 3D models can be used in geodesy for inventory measurements, they fi nd their application in architecture and spatial planning, as well as in many other engineering activities related to the designing of parts, machines, and objects.
Keywords: non-metric cameras • 3D models • visualization
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