Ústav geodézie

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Precise Positioning of Primary System of Geodetic Points by GNSS Technology in Railway Operating Conditions
(MDPI, 2024-04-13) Bureš, Jiří; Vystavěl, Ondřej; Bartoněk, Dalibor; Bárta, Ladislav; Havlíček, Radomír
This article deals with the analysis of the accuracy of the geodetic real-time GNSS measurement procedure used in railway operating conditions in the Czech Republic. The purpose was to deter-mine to what extent the operating conditions affect the accuracy of the measurement result and whether an accuracy of standard deviation x,y = 5 mm in the horizontal plane could be achieved. The use of geodetic GNSS equipment with an IMU unit was also tested. The accuracy obtained in op-erational conditions is compared with the accuracy obtained on a calibration base using the same measurement procedure. The consistency between the accuracy of the primary system (satel-lite-based) and the secondary system (terrestrially measured by the traverse method) is also dis-cussed. The analysis includes the issue of residual inhomogeneities of the uniform transformation key when converted to the Czech national coordinate system S-JTSK. It is shown that a homoge-neous accuracy in coordinate standard deviation better than x,y = 5 mm can be achieved. The results indicate that the accuracy under operational conditions is twothree times worse than the accuracy achieved by the same procedure under ideal conditions on a calibration base. This is due to the non-ideal observing conditions, i.e., horizon occlusion by overlays, surrounding vegetation and multipath effects. It has been shown that the effect of multipath can be reduced by repeating short observations 34 h apart. Older GNSS instruments using an IMU unit in combination with an elec-tronic compass (eCompass) are at risk of a systematic bias of up to several tens of millimeters, which can be detected by rotating the antenna by 180°. The current uniform transformation key used in the Czech Republic for the conversion of GNSS coordinates into the national system has residual ge-ometric inhomogeneities (p = 0.90 to 10 mm/km, sporadically up to 20 mm/km), which metrolog-ically deteriorate the results of the calculation of the terrestrially measured secondary system in-serted into the GNSS measured primary system. Achieving homogeneous accuracy in coordinate standard deviation in a horizontal plane better than x,y = 5 mm has been demonstrated in non-ideal railway operating conditions with increased risk of multipath. The innovative aspect of the approach used is that it simplifies and thus increases the efficiency of the measurement with respect to the availability of GPS, GLONASS, Galileo and BeiDou satellites, as well as reducing the effect of mul-tipath on the noise by repeating the measurement procedure.
Identification and Verification of Geodynamic Risk Zones in the Western Carpathians Using Remote Sensing, Geophysical and GNSS Data
(Springer Nature, 2024-12-19) Pospíšil, Lubomil; Bartoněk, Dalibor; Bureš, Jiří; Švábenský, Otakar
Previous surveys using the remote sensing (RS) method revealed significant structures in the area of the Western Carpathians. It has not yet been possible to verify and explain the results of these surveys, even though all the phenomena are regional in nature and show many morphological features that clearly indicate recent activity and deformations, including current earthquake foci. The aim of the article was to verify these phenomena and compare them with new findings. A method of combining geomorphological data with satellite image analysis and verification using Global Navigation Satellite Systems (GNSS) and geophysics data was used. In this work, results are presented confirming the existence of a previously identified nonlinear structure—the "gravity nappe" in the western part of the Low Tatras, and the largest tectonic system Muráň—Malcov is analyzed in detail. Similar structures and tectonic zones, on a smaller scale, can also be found in other areas of the Carpathians. For example, the gravity structure in the Lesser Carpathians and the Ukrainian flysch Carpathians or the linear boundaries interpreted as tectonic systems—the Myjava-Subtatrans, Hron and Transgemerian tectonic zones. Recent movement trends have been confirmed by newly unified data from EUREF Permanent Network (EPN) stations and GNSS campaigns carried out in the last two decades in the given area. Both types of analyzed structures are directly related to the occurring foci of earthquakes.
Long-term deformation measurements of atypical roof timber structures
(FCE CTU Prague, 2014-12-01) Bureš, Jiří; Švábenský, Otakar; Kalina, Marek
The paper includes conclusions from evaluation of results obtained from long-term measuring of innovative atypical roof timber structures. Based on the results of measurements of vertical and horizontal deformation components it is possible to analyze the real behaviour of structures in given conditions. By assessing deformations in various stages, including particularly external and internal environment temperatures, relative air humidity and moisture content of wood, decisive parameters for real structure behaviour can be established. The data are processed from period 2001 – 2013.
New velocity analysis in geodynamic network Sněžník based on GNSS measurement reproces- sing using reprocessed IGS products
(IRSM AS CR, 2014-03-21) Puchrik, Lukáš; Švábenský, Otakar; Pospíšil, Lubomil; Weigel, Josef
The availability of IGS reprocessed products enabled comprehensive reprocessing of all GNSS data from the Local Geodynamic SNĚŽNÍK network over period 1997-2011. All calculations were performed using the Bernese GPS Software 5.0. The absolute method of Precise Point Positioning (PPP) was used for the first time within the network providing interesting results. Tha main evaluation of recent movement tendencies was done using the common relative method where the nearest IGS stations were used as reference.
Problems of Creation and Usage of 3D Model of Structures and Theirs Possible Solution
(MDPI, 2020-01-20) Bartoněk, Dalibor; Buday, Michal
This article describes problems that occur when creating three-dimensional (3D) building models. The first problem is geometric accuracy; the next is the quality of visualization of the resulting model. The main cause of this situation is that current Computer-Aided Design (CAD) software does not have sufficient means to precision mapping the measured data of a given object in field. Therefore the process of 3D model creation is mainly a relatively high proportion of manual work when connecting individual points, approximating curves and surfaces, or laying textures on surfaces. In some cases, it is necessary to generalize the model in the CAD system, which degrades the accuracy and quality of field data. The article analyzes these problems and then recommends several variants for their solution. There are described two basic methods: using topological codes in the list of coordinates points and creating new special CAD features while using Python scripts. These problems are demonstrated on examples of 3D models in practice. These are mainly historical buildings in different locations and different designs (brick or wooden structures). These are four sacral buildings in the Czech Republic (CR): the church of saints Johns of Brno-Bystrc, the Church of St. Paraskiva in Blansko, further the Strejc’s Church in Židlochovice, and Church of St. Peter in Alcantara in Karviná city. All of the buildings were geodetically surveyed by terrestrial method while using total station. The 3D model was created in both cases in the program AUTOCAD v. 18 and MicroStation.

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