Celem realizacji badań opisanych w ramach niniejszej monografii było opracowanie modelu współczesnych deformacji powierzchni litosfery na obszarze Europy Środkowej i Polski na podstawie sieci permanentnych stacji geodezyjnych ASG-EUPOS i EPN (EUREF Permanent Network), analiza pod kątem ich przydatności do badań dynamiki powierzchni Ziemi, jak również konstrukcja modelu analitycznego na bazie informacji geologicznych. Na podstawie prędkości poziomych w układzie ITRF2008 ponad 300 stacji leżących na terenie Europy stworzono ciągły model odkształceń poziomych przy pomocy zmodyfikowanej metody najmniejszych kwadratów i zaprezentowano w postaci głównych ich składowych (rozciągania i ściskania) w siatce regularnej. Przeprowadzono jednocześnie analizę wiarygodności wyznaczeń za pomocą dwóch kryteriów: kątowego i radialnego rozmieszczenia stacji (punktów pomiarowych) wokół węzła, w którym deformacje są wyznaczane. Porównanie odkształceń wyliczonych dla terenu całej Europy dokonano z wyznaczeniami przeprowadzonymi niezależnymi metodami i zebranymi w bazie World Stress Map (WSM) otrzymując dużą zbieżność. Część analityczna projektu rozpoczęła się od przeglądu obszarów i struktur aktywnych neotektonicznie w celu wyznaczenia przebiegu stref nieciągłości mechanicznej litosfery na terenie Europy Środkowej, będących podstawą konstrukcji analitycznego modelu deformacji i naprężeń na terenie Europy Środkowej. Wykonano go za pomocą metody elementów skończonych (MES). Bezpośrednie porównanie obydwu skonstruowanych modeli nie jest do końca możliwe z uwagi na inny rodzaj wielkości podlegających modelowaniu. Model analityczny stworzony na bazie metody elementów skończonych pozwolił na wyznaczenie głównych kierunków i wartości naprężeń, podczas gdy model wykorzystujący dane geodezyjne – odkształceń. Porównanie kierunków wyznaczonych z obydwu modeli pokazało zbieżności w rejonach o największych współcześnie zarejestrowanych ruchach neotektonicznych. Przyczyną różnic w rejonach o niskiej aktywności tektonicznej, jak np. rejon Europy Środkowej, może być fakt, iż wyliczane wielkości są na poziomie wiarygodności ich wyznaczenia. Podkreślić należy, że sporządzony model geomechaniczny stanowi najbardziej ogólne przybliżenie rozkładu naprężeń i odkształceń litosfery, niemniej przy obecnym stanie badań w Polsce nie można skonstruować modelu bardziej realistycznego mechanicznie.
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Observations recorded by the Global Positioning System (GPS) permanent stations are currently an essential source of data about large-scale and local phenomena that occur on the Earth’s surface and
in the atmosphere as well. During the re-processing of GPS data, we estimate the GPS position time series or the Zenith Total Delay (ZTD) time series. All series have to be modelled with attention paid to trend and seasonal signals with changing/constant amplitude. Stochastic part or residuals are recognized to be close to flicker noise for GPS series or to autoregressive process for ZTD data. Time series may be affected much by employed method. It may totally change a character of residuals from coloured noise into less correlated character of white noise. In this way, the errors of trend and amplitudes of seasonal signals will be underestimated and may lead to wrong interpretations. Most time series contain a seasonal signal in a form of annual and semi-annual period that are routinely modelled by two periodic signals with constant amplitudes using the Weighted Least-Squares (WLS). However, in reality the amplitude of these seasonal signals varies slightly over time and this should be taken into account. Although this variability reach few millimetres at maximum, it may introduce additional temporal correlation and will lead to overestimation of trend. The time-varying signals have been so far modelled with: Kalman Filter (KF), Chebyshev Polynomials (CP), Singular Spectrum Analysis (SSA) or Wavelet Decomposition (WD). Each of above-mentioned methods have been already marginally described for amount of power that is artificially removed from stochastic part (or noise) together with the seasonal signal. The proposed research is aimed at answering the question: how should we model seasonal signals to keep at the same time the stochastic properties of data intact. In this proposal, we will verify the main research hypothesis which reads as follows: “seasonal signals should be modelled as time-varying and removed from geodetic time series with no artificial loss in power”. Moreover, we are taking the working hypothesis that: “a combination of a modified Wiener Filter and a character of coloured noise allows to separate noise from a real geophysical signal that changes over time”. This hypothesis will be verified by 1) comparison of commonly used approaches to model the seasonal part assuming its constancy and variability in time (WLS, KF, SSA & WD) and by 2) employing an innovative approach, which we will introduce within project, based on Adaptive Wiener Filter (AWF). In the following project, we assume that a way which AWF is being constructed must provide the optimum separation between real geophysical signal from observational noise. In this turn, no artificial loss in power and no artificial underestimation of trends and their uncertainties will be assured. ... [more] View project
This research focuses on verification of the main research hypothesis which states as follows: "a proper recognition of stochastic part of ZTD (Zenith Total Delay) time series is indispensable to r
eliably estimate the parameters of deterministic part and their uncertainties (including trend used in analyses of climate change)". This hypothesis will be verified by comparison to common approach which includes only white process and is widely used to date by geodetic community to model the GNSS-derived ZTD time series. This innovative approach based on autoregressive process, which is going to be used for homogenously reprocessed and properly homogenized ZTD series, will result in new values of ZTD trends with their uncertainties that can be further interpreted in climate studies. ... [more] View project
Due to the series length, availability of observations and density of stations (more than 20 years of observations collected at 10 000 sites on the Earth), the position time series collected at the
Global Positioning System (GPS) permanent stations have become an inexhaustible source of knowledge about phenomena happening at and inside the Earth. Velocities of permanent stations are interpreted as tectonic plate movement or possible earthquakes. Beyond the linear trend, also seasonal variations arising from hydrological, atmospheric or oceanic loadings can similarly influence time series collected at the nearby stations. Having modelled the deterministic part of the GPS position time series, which was mentioned above, the residuals (or a so-called noise) are obtained. Former researches showed that the GPS position time series are best characterized by the power-law noise with spectral index close to flicker noise. However, some part of residuals corresponds to the influence that the mismodelled large scale phenomena have on the GPS observations. This mismodelled part is being transferred to the individual observations and is referred to as a Common Mode Error (CME). The existence of both noises and CME will cause the overestimation of errors of velocities. Moreover, the inefficiently modelled seasonal part will result in an increase of: an auto-correlation of series, the noise level and indirectly also in an increase of velocity error. The main goal of the proposed project is then to provide new estimates of velocity field errors, being determined when spatially and temporally correlated signals in a form of seasonal variations and CME were removed from geodetic observations. Therefore, the research hypothesis of this project reads as follows: “spatially and temporally correlated signals need to be removed from GPS position time series before the reliability of permanent station’s velocity required for creation of reference frame is achieved”. Further, the authors make use of auxiliary hypothesis which is: “probabilistic Principal Component Analysis can be successfully applied to GPS position time series”. The authors propose to employ probabilistic Principal Component Analysis (pPCA), which has never been employed before to geodetic time series. As is supposed, pPCA can bring an innovation to how the CME are estimated in a way it handles missing data. Up until now, the stations with many missing data, or those which did not overlap each other were removed from CME estimation and therefore, the values of CME were not reliable. pPCA assumes that the values are missing at random through the data set. Therefore, the GPS position time series may start and end in a different independent epochs and also, these epochs do not have to overlap with each other. At a time of increasing number of newly established GPS stations, this assumption seems to be crucial so as not to lose information or false estimates due to missing observations, removed stations or interpolation. ... [more] View project January 2009
Antenna changes at GNSS reference stations frequently produce discontinuities in their coordinate time series, especially in the height component. These coordinate shifts are mainly caused by changes of carrier-phase multipath effects and also, but usually to a smaller extend, by errors in the antenna phase center corrections. A monitoring method was developed and successfully tested, which
... [Show full abstract] requires additional GNSS observations from a local, temporary reference station. Changes of carrier-phase measurement errors due to the antenna exchange are determined and stored in L1 and L2 phase maps. The paper deals with the application of this new technique to 13 recent antenna changes in a network of permanently operating reference stations. Based on the modeling results we are able to present a detailed analysis of the effects of the antenna surroundings on discontinuities of station coordinate time series. Read more Article Full-text available January 2015 · Kosmìčna Nauka Ì Tehnologìâ
The possibility of constructing regional maps of the iono-
sphere TEC with a spatial resolution of 50—100 kilometers
according to the GNSS network base stations is justified.
The developed technique allowed detecting the presence of
stationary irregularities in the mid-latitude ionosphere, with
a spatial scale of about three hundred kilometers and time of
existence about two hours.
View full-text Conference Paper Full-text available June 2014
The velocities derived from permanent GNSS stations play more and more significant role nowadays. Therefore their reliable estimation becomes crucial. These velocities and their uncertainties are involved in the kinematic reference frames determination and numerous analyses and interpretations in the geodynamic studies. They are commonly determined with the Least Squares Estimation (LSE) by
... [Show full abstract] fitting the trend into changes of topocentric components (North, East and Up). The goodness of fit of such a trend, interpreted as velocity uncertainty, is estimated basing on the differences between the topocentric changes and modelled values. In this research, the changes of daily topocentric components from ASG-EUPOS and selected EPN stations were used. We investigated the goodness of fit of the linear regression line into topocentric components for velocity determination. It was estimated with the coefficient of determination (referred to as R2) and residual error (RE). The R2 values close to 1 prove the well fitted LS line into the time series, while lower values are the effect of unremoved (or improperly removed) outliers, offsets and seasonal components. This clearly demonstrates how determination of the velocity of permanent stations can suffer from the correct data pre-analysis. View full-text Article Full-text available January 2011
The paper presents current activities of the Centre of Applied Geomatics (CAG), Warsaw Military University of Technology in the frame of EPN (EUREF Permanent Network). The Centre is the research unit, which operates within Military University of Technology. The main field of interests of its members covers GNSS (Global Navigation Satellite Systems) data processing and analysing. Since the end of
... [Show full abstract] 2009 CAG runs the newest, seventeenth Local Analysis Centre (LAC) of EUREF Permanent Network (EPN), which is a science-driven network of continuously operating GNSS reference stations with precisely known coordinates. The network processed by CAG consists of 114 sites distributed all over the Europe. The processing strategy is similar for all LACs, the weekly and daily processing is performed on the computer cluster specially designed for these purposes. Besides the Centre is one of the leaders in the EPN re-processing project. It is the venture for computing consistent precise coordinates, velocities and by products (e.g. troposphere parameters) based on the EPN in support of the ETRS89 (European Terrestrial Reference System) using identical standards for the entire period of time. In 2008 CAG has successfully completed the test re-processing of the full European Permanent Network (EPN), consisting of the historical observation series for the period between 1996-2007 for almost 200 stations. CAG was one of two European research centres (at the same time another test reprocessing with a different strategy was performed at the Royal Observatory of Belgium) which were able to carry out this task. The test reprocessing is a starting point for the elaboration of an optimal processing strategy for the final, official EPN reprocessing. To increase the credibility of GNSS solutions in 2009, the work began on getting alternative software GAMIT/GLOBK. The comparison between processing results from these two software is essential for proper geodynamical and geophysical interpretation of the results. According to the agreement with the Head Office of Geodesy and Cartography the one of the CAG's task is the monitoring of the long and short term stability of the Polish multifunctional precise satellite positioning system ASG-EUPOS. The presentation shows the current activities of the CAG in the frame of EPN, presents the newest results of precise solutions and the strategy used for GNSS (GPS/GLONASS) data processing. View full-text Article Full-text available January 2010 · Acta Geodynamica et Geomaterialia
The paper presents the results of research related to the application of GNSS solutions in short observational periods in geodynamical investigations. Authors used the 3-hour solution appointed from hour-long interval of about 30 chosen stations on mountainous terrains from over 100 which were worked out. The main aim was to check the correctness of such solutions by the comparison with the daily
... [Show full abstract] ones. Some outliers in East component could testify, that tropospheric or ionospheric models used in the data adjustment are not sufficient for so short-time solutions. The second principal problem, which was considered in the present work is the ability to detect diurnal and sub-diurnal oscillations in changes of permanent stations' coordinates. Results show unambiguously, that such oscillations appear in all analysed stations. In the paper there are examples of stations with dominant oscillations in different frequencies. The clear homogeneous in the frequencies was not found among any group of stations. It is therefore difficult to affirm, if their origin comes purely from the geodynamical phenomena. surface provided by gravity satellite missions. It shows that a variety of sensor systems, mission characteristics, and tracking systems have to be combined with utmost precision (Plag and Pearlman, 2009). The interconnections between mass transport processes, and the relations between observable parameters of gravity and geometry and the different processes are sketched in Figure 2. View full-text Conference Paper Full-text available June 2014
The stochastic part (noises) of the GPS-derived time series has a direct impact on the uncertainties of the linear parameters estimated from this data. The noises are commonly analysed with the Maximum Likelihood Estimation (MLE) that is stated as being the most precise method for this purpose. Furthermore it is a very powerful method for different practical research e.g. investigation of
... [Show full abstract] permanent GNSS station’s stability. In general, the noises are recognized as the power-law processes characterized by the spectral index κ and the amplitude A. There are three integer values of spectral indices, that stand for the special cases of noises: white noise, flicker noise and random-walk. The most of the papers showed, that noises in the GPS time series are the closest to flicker one, which is the effect of mis-modelled satellite orbits, Earth Orientation Parameters or large scale atmospheric influences. Besides, the amplitudes of noise reveal the latitude dependence for vast networks. In this research, the daily changes of topocentric coordinates (North, East and Up components) in the ITRF2005 from the set of EPN (EUREF Permanent Network) stations were used. The time series were obtained by the Bernese 5.0 processing (“repro1” project) performed in the Centre of Applied Geomatics that cooperates at the Military University of Technology as one of the 16 EPN Local Analysis Centres (MUT LAC). The time series were pre-analysed with the median absolute deviation (MAD) criterion and sequential t-test algorithm (STARS) to remove outliers and offsets. The stochastic part of GPS time series was analysed with the MLE method with white plus flicker noise model assumed a-priori. As the result, the amplitudes of the aforementioned noises for all of the EPN stations were estimated. The EPN network is located between the meridians of 27° N and 80° N, what gives the 53 degrees of latitude. The paper presents the comparison of noise amplitudes in relation to the geographical location of permanent GPS stations. View full-text Last Updated: 05 Jul 2022
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