Aerial photogrammetry was chosen as an additional observation method of the subsidence depression that was created above exploited coal mining panels near Karviná. While individual points of a permanent observation network were repeatedly surveyed by GNSS, the whole subsidence depression was surveyed by the aerial photogrammetry. As this method was applied three times (during three years) we can compare its results in individual years and observe the major surface changes on the undermined area. Also, a comparison was realized between the points’ coordinates gained from both aerial photogrammetry and GNSS. The results show that the method of aerial photogrammetry enriches and complements the GNSS observation in monitoring the spatial development and shape of the subsidence depression, especially in the areas of active recultivation., Vlastimil Kajzar, Hana Doležalová, Kamil Souček and Lubomír Staš., and Obsahuje bibliografii
Using GNSS method, fixed points of an observation network were repeatedly surveyed on the surface of the undermined area. Below the surface, at the depth of c. 1 km, there were four mining panels exploited subsequently. The main reaction of the surface points to the changes in the rock massif and the movement of the points were different, according to their surface position, local geo-mechanical conditions etc. This paper analyses the time-dependence of the surface points mining subsidence and horizontal movements on the progress of the exploitation., Hana Doležalová, Vlastimil Kajzar, Kamil Souček and Lubomír Staš., and Obsahuje bibliografické odkazy
This research evaluates the potential benefits of the tightly combined processing of a global navigation satellite system together with the additional ranging observations from a satellite based augmentation system. In specific, the experiment presents performance of precise instantaneous single-frequency positioning based on European Galileo and EGNOS navigation systems. Due to currently low number of Galileo satellites, the test observational data were obtained with hardware GNSS signal simulator. All calculations were performed with in-house developed software - GINPOS. The results show that it is possible to obtain improvement in the accuracy and reliability of single-frequency precise positioning when including observations from SBAS systems. However, one must take in to account that at middle latitudes EGNOS satellites are observed at low elevations what results in higher atmospheric errors affecting its signals., Jacek Paziewski, Paweł Wielgosz and Marta Krukowksa., and Obsahuje bibliografické odkazy
The use of Continuously Operating Reference Stations, both singly and as part of an active network, is widely employed in surveying, engineering and other geomatics applications, achieving high accuracy positioning even in real time. With an active network the measurements of the reference stations are processed jointly in order to model the errors and compute network RTK corrections. Due to distance dependent errors (ionospheric and tropospheric delays), single base RTK positioning accuracy decreases with increased baseline length. However, the network solution (NRTK) retains the accuracy and the time to fix ambiguities (TTFA) at a constant level. This study aims to contribute to the scientific research on real time positioning based on active networks. In Southern Spain, ERGNSS, a national CORS network that provides GNSS data for post-processing and real time single- b ased reference station corrections, shares territory with the Andalusian Positioning Network (RAP), a local active network. RAP provides network an d single-based RTK corrections. In order to analyze the quality of real time positioning based on both networks, several tests have been performed on a sample of test points. The reference frame, the time to fix ambiguity resolution, precision, accuracy and repeatability of RTK positioning are considered as the evaluation parameters. The results confirm that the RAP network complements the precise positioning services provided by the ERGNSS network, ensuring accurate real time positioning, full cove rage and reliable positioning services in the Andalusian Community., Mª Selmira Garrido, Antonio J. Gil and Rafael Gaitán., and Obsahuje bibliografické odkazy
Precise Point Positioning (PPP) has been considered a powerful method for GNSS data processing. The essential input products, such as precise satellite orbits and clocks, are provided within the International GNSS Service (IGS) with a sufficient quality for estimating receiver coordinates with centimeter level accuracy. However, the IGS satellite clocks enable users to estimate ambiguities only as float values. An additional product for satellite phase biases is necessary for an integer ambiguity resolution (PPP AR). Another approach is the backward smoothing algorithm utilizing already precise and converged parameters for improving those parameters estimated at previous epochs. All the three approaches for ambiguity estimation are compared and assessed in terms of advantages and disadvantages, achieved coordinates precision, and flexibility. The comparison are performed through a processing of GNSS data from selected IGS permanent stations during 30 days in 2018, and a processing of high rate GNSS observations of the station STRF in Greece collected during the seismic event occurred on October 25, 2018. The backward smoothing improved the float solution similarly like the PPP AR, and therefore can be considered an alternative approach providing easier implementation and no dependency on additional satellites products. We utilized two different products for phase biases in the PPP AR, namely Integer Recovery Clocks (IRC) provided by the Centre National d’Études Spatiales/Collecte Localisation Satellites (CNES/CLS) analyses center and Fractional Cycle Biases (FCB) which were estimated at the Geodetic Observatory Pecny (GOP) analyses. The IRC is based on the assimilation phase biases into satellite clocks, while the FCB products are distributed in terms of wide-lane and narrow-lane biases. A similar accuracy obtained from our comparison indicates an interoperability of products when using different strategies and even different software.
The development of knowledge on geodynamic processes is one of the most important issues in the Earth’s science. Over decades, geodetic techniques have been applied to study the geodynamics. The Global Navigation Satellite Systems (GNSS) have been reliably used for monitoring geodynamic processes. The satellite gravimetric missions such as GRACE (Gravity Recovery And Climate Experiment) and GRACE Follow-On (GRACE-FO) missions have provided numerous valuable information concerning temporal mass variations within the Earth system which can subsequently be converted to surface deformations of the Earth. The main aim of this study is to compare vertical deformations of the Earth's surface over the area of SouthEastern Poland obtained from GNSS data with the corresponding ones determined from GRACE data. The GNSS data for the period between 2008 and 2013 from 25 permanent GNSS stations operating in South-Eastern Poland and the latest release of GRACE-based Global Geopotential Models (GGMs) were used. GNSS data and GRACE-based GGMs were processed with the GAMIT/GLOBK and the IGiK‒TVGMF (Institute of Geodesy and Cartography - Temporal Variations of Gravity/Mass Functionals) packages, respectively. The results obtained indicate that monthly vertical deformations of the Earth’s surface determined using GNSS data are generally in a good agreement with the corresponding ones obtained from GRACE satellite mission data. Coefficients of correlation between these vertical deformations range from 0.60 to 0.90 and standard deviations of their differences are in the range of 2.6 - 5.7 mm., Walyeldeen Godah, Malgorzata Szelachowska, Jagat Dwipendra Ray and Jan Krynski., and Obsahuje bibliografii
A Global Navigation Satellite System (GNSS) software library called G-Nut has been devel oped at the Geodetic Observatory Pecný (GOP) since 2011. Several applications built of the library will be provided as an open source in 2013 and consequently users are able to modify source code and use it for processing their own data free of charge. The main purpose of the project is to create a programming package suitable for implementing various end-user a pplications such as kinematic position estimation, long-term permanent station coordinates monitoring, zenith tropospheric delay estimation, satellite clock estimation and others. The library is written in C++ programming language following the object-oriented concept. Basic class structure implementing inputs/outputs and product/d ata containers support both real-time and post-processing modes. Integration of all available global navigation satellite systems (GPS, GLONASS, Galileo, BeiDou, QZSS) as well as new tracking signals is properly handled. The configuration is governed through the XML format. The estimation model currently supports the least square adjustment, the Kalman and square root covariance filtering methods based on processing undifferenced data and fixed precise orbit and clock products. The estimated state vector includes receiver coordinates and clocks, troposphere zenith path delays and initial carrier phase ambiguities. The first applications based on G-Nut library are shown with examples for off-line/online kinematic/static precise point positioning and ultra-fast troposphere estimation., Pavel Václavovic, Jan Douša and Gabriel Györi., and Obsahuje bibliografické odkazy
A new observation network has been built to observe the surface manifestations of undermining at Gabriela locality. This locality lies in the Czech part of the Upper Silesian Coal Basin and the history of the hard coal underground exploitation is more than 150 years long here. Recently, the last coal mining panel was started to be exploited here. Its location and mining parameters are very suitable for the analysis of the actual and future surface changes caused by undermining. The fixed points of the observation network are surveyed by geodetic GNSS me thod. This method enables the evaluation of both vertical subsidence and horizontal displacements. Such complex evalua tion of processes on the surface of the undermined territory makes it possible to understand the progress of the subsidence depression and to capture the final phase of the surface undermining changes, i.e. the phase of the subsidence decline., Vlastimil Kajzar, Hana Doležalová, Kamil Souček and Lubomír Staš., and Obsahuje bibliografické odkazy
Latest studies of recent geodynamic movements going on major geological structures of the Sněžník metamorphic unit are closely related to geodetic satellite measurements, especially to permanent and ep och GNSS satellite methods. For this reason the Institute of Geodesy, Faculty of Civil Engineering, Brno University of Technology (IG FCE-BUT) continues measurements in Local Geodynamic Sněžník Network (LGSN) which was established in 1992 in Czech-Polish cooperation for the purpose of lithosphere movement monitoring. A special attention was devoted to detection of possible displacements of the local blocks of Králický Sněžník Massif. The results confirm the significant horizontal and vertical movements within relatively small territory. All these and other detected contemporary geodynamic phenomena are presented and discussed., Otakar Švábenský, Josef Weigel and Lubomil Pospíšil., and Obsahuje bibliografické odkazy
Changes in the position of the GNSS receiver antenna phase centre are still one of the dominant error sources associated with the measuring station. The preferred method of solving the problem is modeling antenna phase centre variations (PCV). Such models are available in igs05.atx, igs08.atx or igs14.atx files, among others. Due to different methods of antenna calibration (chamber calibration, relative field calibration, absolute field calibration) and different types of models (mean, individual), depending on the GNSS observation processing product used, there may occure differences in the estimated parameters, including station coordinates. In this paper, the results of GNSS observation processing using the models included in the igs08.atx and igs14.atx files for 12 EPN and ASG-EUPOS stations were analysed, both for daily and sub-daily time series of PPP solutions. The obtained results show that switching from the igs08.atx to igs14.atx (for the selected stations) induces differences in the vertical component, reaching up to ± 3 mm.