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1
Content available Research on gravity field modelling and gravimetry in Poland in 2019–2022
Krynski Jan, Dykowski Przemysław, Godah Walyeldeen, Szelachowska Małgorzata
Advances in Geodesy and Geoinformation
|
2023
|
Vol. 72, no. 2
art. no. e46, 2023
EN
The article presents the reviewed and summarised research activities of the Polish research groups on gravimetry and gravity field modelling in the period of 2019–2022. It contains the results of absolute gravity surveys for the maintenance of the international gravity reference level in Poland and Europe, and for geodynamic research with an emphasis on metrological aspects. It also contains relative gravimetry issues as well as the results of marine gravity surveys in the southern Baltic Sea. Non-tidal gravity changes were extensively investigated. Long-term gravity variations were monitored at the Borowa Gora Geodetic-Geophysical Observatory and in a few other locations in Poland. The contribution of gravimetric records to seismic studies was investigated. Temporal variations of the gravity field from GRACE (Gravity Recovery and Climate Experiment) and GRACE-FO (GRACE Follow-On) data, in particular, deformations of the Earth’s surface as well as temporal variations of heights, total water storage and groundwater storage were investigated. Moreover, GRACE-based products and the performance of monthly Global Geopotential Models (GGMs) were a subject of research. GGMs developed in last years were evaluated. The research on developing new approaches in geoid modelling and their validation was conducted. New regional and local geoid models were determined for Poland and Ethiopia. The use of different techniques for estimating the absolute sea level at sites of the selected network in the Baltic Sea was investigated.
2
Content available remote Stress feld estimation by the geoid undulations of the Samos Kuşadası Bay and implications for seismogenic behavior
Oruç Bülent, Balkan Emir
Acta Geophysica
|
2021
|
Vol. 69, no. 3
1137--1149
EN
The strong earthquake with magnitude 6.9 occurred ofshore at the northernmost edge of the Samos Island and was strongly felt in the north Aegean islands and İzmir metropolitan city. In this study, the effective elastic thicknesses of the lithosphere and seismogenic layer thickness were correlated with each other in order to understand the nature of the earthquakes. We determined that the upper and lower depth limits of seismogenic layer are in a range of 5–15 km, meaning that only the upper crust is mostly involved in earthquakes in the study area. The fact that seismogenic layer and effective elastic thicknesses are close to each other indicates that the earthquake potential may be within the seismogenic layer. Following that, we estimate the stress feld from the geoid undulations as a proxy of gravity potential energy in order to analyze the amplitude and orientation of the stress vectors and seismogenic behavior implications. The discrete wavelet transform has been carried out to decompose the isostatic residual gravity anomalies into horizontal, vertical and diagonal detail coefcients. The results delineated edges of gravity anomalies that reveal some previously unknown features.
3
Content available remote Modernizacja plus
Banasik Piotr, Bujakowski Kazimierz
Geodeta : magazyn geoinformacyjny
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2019
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nr 11
24--26
4
Content available remote Mieszanie w układach
Kadaj Roman
Geodeta : magazyn geoinformacyjny
|
2019
|
nr 10
34--35
5
Content available Research on gravity field modelling and gravimetry in Poland in 2015–2018
Krynski Jan, Dykowski Przemysław, Olszak Tomasz
Geodesy and Cartography
|
2019
|
Vol. 68, no. 1
31--63
EN
Activities of the Polish research gSDroups concerning gravity field modelling and gravimetry in a period of 2015–2018 are reviewed and summarised in this paper. The summary contains the results of research on the evaluation of GOCE-based global geopotential models (GGMs) in Poland and geoid modelling. Extensive research activities are observed in the field of absolute gravity surveys, in particular for the maintenance of national gravity control in Poland, Sweden, Denmark, the Republic of Ireland and in Northern Ireland as well as for geodynamics with special emphasis on metrological aspects in absolute gravimetry. Long term gravity variations were monitored in two gravimetric laboratories: the Borowa Gora Geodetic-Geophysical Observatory, and Jozefoslaw Astrogeodetic Observatory with the use of quasi-regular absolute gravity measurements as well as tidal gravimeter records. Gravity series obtained were analysed considering both local and global hydrology effects. Temporal variations of the gravity field were investigated using data from GRACE satellite mission as well as SLR data. Estimated variations of physical heights indicato the need for kinematic realization of reference surface for heights. Also seasonal variability of the atmospheric and water budgets in Poland was a subject of investigation in terms of total water storage using the GLDAS data. The use of repeatable absolute gravity data for calibration/validation of temporal mass variations derived from satellite gravity missions was discussed. Contribution of gravimetric records to seismic studies was investigated. The bibliography of the related works is given in references.
6
Content available Approximation of the spheroid offset surface and the torus offset surface
Borowska A.
Journal Biuletyn of Polish Society for Geometry and Engineering Graphics
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2018
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Vol. 31
3--10
EN
In this paper the issue of approximation of the spheroid offset surface off(S(u, v); s) at distance s by the spheroid surface S1(u, v) is considered. The problem of determining the appropriate parameter values for the spheroid offset surface off(S(u, v); s) is important due to the numerous practical applications of the spheroid as a mathematical model of the Earth. We present the algorithm which gives the appropriate parameter values for the spheroid Surface S(u, v) and its offset surface off(S(u, v); s).
PL
W niniejszej pracy rozważa się kwestię aproksymacji powierzchni offsetowej elipsoidy off(S(u, v); s) o odległości s przez elipsoidę S1(u, v). Umiejętność doboru odpowiednich wartości parametrów dla powierzchni elipsoidy i jej offsetu jest istotna ze względu na liczne zastosowania praktyczne elipsoidy spłaszczonej jako matematycznego modelu kuli ziemskiej. Prezentujemy algorytm, który zwraca odpowiednie wartości parametrów dla powierzchni elipsoidy i jej offsetu.
7
Content available Determination of correlation coefficient between geoid-to-quasigeoid separation calculated by the satellite data in Sjöberg’s equation and GPS/Levelling method
Eshaghzadeh A., Kalantari R. A., Hekmat Z. M.
Geodesy and Cartography
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2018
|
Vol. 67, no. 2
179--192
EN
In this paper, two techniques for calculating the geoid-to-quasigeoid separation are employed. One of them is GPS/Levelling customary method as a criterion where the geoid undulation and height anomaly are computed by subtracting the ellipsoid height attained via GPS from the orthometric height and normal height, respectively. Another approach is Sjöberg’s equation. We have used of the ICGEM website for definition of the variables of the Sjöberg’s equation, as the applied reference model is the EGM2008 global geopotential model and WGS84 reference ellipsoid. The investigations are performed over the stations of the GPS/Leveling network related to three selected areas in desert, mountain and flatland namely the Lout, Zagros and Khuzestan in Iran and afterward the correlation coefficient between the geoid-to-quasigeoid separation calculated using the satellite data in Sjöberg’s equation and GPS/Levelling method is estimated. The results indicate a straight correlation between the estimated separations from the two methods as its value for the Lout is 0.754, for the Zagros is 0.497 and for the Khuzestan is 0.659. consequently, using the satellite data in Sjöberg’s equation for the regions where there are not the GPS/Levelling and land gravity data, specially for the even areas, yield a satisfactory response of the geoidto-quasigeoid separation.
8
Content available remote On the analysis of temporal geoid height variations obtained from GRACE-based GGMs over the area of Poland
Godah W., Szelachowska M., Kryński J.
Acta Geophysica
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2017
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Vol. 65, no. 4
713--725
EN
Temporal mass variations in the Earth system, which can be detected from the Gravity Recovery and Climate Experiment (GRACE) mission data, cause temporal variations of geoid heights. The main objective of this contribution is to analyze temporal variations of geoid heights over the area of Poland using global geopotential models (GGMs) developed on the basis of GRACE mission data. Time series of geoid height variations were calculated for the chosen subareas of the aforementioned area using those GGMs. Thereafter, these variations were analyzed using two different methods. On the basis of the analysis results, models of temporal geoid height variations were developed and discussed. The possibility of prediction of geoid height variations using GRACE mission data over the area of Poland was also investigated. The main findings reveal that the geoid height over the area of Poland vary within 1.1 cm which should be considered when defining the geoid model of 1 cm accuracy for this area.
9
Content available Gravity field modelling and gravimetry
Krynski J.
Geodesy and Cartography
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2015
|
Vol. 64, no. 2
177--200
EN
The summary of research activities concerning gravity field modelling and gravimetric works performed in Poland in the period of 2011-2014 is presented. It contains the results of research on geoid modelling in Poland and other countries, evaluation of global geopotential models, determination of temporal variations of the gravity field with the use of data from satellite gravity space missions, absolute gravity surveys for the maintenance and modernization of the gravity control in Poland and overseas, metrological aspects in gravimetry, maintenance of gravimetric calibration baselines, and investigations of the nontidal gravity changes. The bibliography of the related works is given in references.
10
Content available A new geoid for Brunei Darussalam by the collocation method
Lyszkowicz A., Birylo M., Becek K.
Geodesy and Cartography
|
2014
|
Vol. 63, no. 2
183--198
EN
Computation of a new gravimetric geoid in Brunei was carried out Rusing terrestrial, airborne and altimetric gravity data and the EGM08 geopotential model by the collocation method. The computations were carried out by the „remove-restore” technique. In order to have better insight in the quality of input data the estimation of accuracy of the gravity data and geoid undulations from GPS/levelling data was carried out using EGM08 geopotential model. It shows a poor quality of GPS/levelling data. Result of the computation is the gravimetric geoid for the territory of Brunei computed by collocation method with an accuracy estimated below of ±0.3 m.
PL
Wyznaczenie przebiegu nowej geoidy na obszarze Brunei zostało zrealizowane z wykorzystaniem lądowych, lotniczych i altimetrycznych danych grawimetrycznych oraz modelu geopotencjału EGM08 metodą kolokacji. Obliczenia zostały przeprowadzone z wykorzystaniem techniki „removerestore”. W celu uzyskania lepszego wglądu, w jakość danych wejściowych oszacowano dokładność danych grawimetrycznych i geometrycznych odstępów geoidy od elipsoidy na punkach sieci GPS wykorzystując do tego celu model geopotencjału EGM08. Z przyprowadzonych oszacowań wynika przede wszystkim niska dokładność danych GPS/niwelacja. Wynikiem przeprowadzonych obliczeń jest grawimetryczna geoida dla obszaru Brunei, obliczona metodą kolokacji, której dokładność szacuje się poniżej ±0.3 m.
11
Content available Estimation of covariance parameters for GNSS/leveling geoid data by Leave-One-Out validation
Jarmołowski W.
Technical Sciences / University of Warmia and Mazury in Olsztyn
|
2013
|
nr 16(4)
291--307
EN
The article describes the estimation of covariance parameters in Least Squares Collocation (LSC) by Leave-One-Out (LOO) validation, which is often considered as a kind of cross validation (CV). Two examples of GNSS/leveling (GNSS/lev) geoid data, characterized by different area extent and resolution are applied in the numerical test. A special attention is focused on the noise, which is not correlated in this case. The noise variance is set to be homogeneous for all points. Two parameters in three covariance models are analyzed via LOO, together with a priori noise standard deviation, which is a third parameter. The LOO validation finds individual parameters for different applied functions i.e. different correlation lengths and a priori noise standard deviations. Diverse standard deviations of a priori noise found for individual datasets illustrate a relevance of applying LOO in LSC. Two examples of data representing different spatial resolutions require individual noise covariance matrices to obtain optimal LSC results in terms of RMS in LOO validation. The computation of appropriate a priori noise variance is however difficult via typical covariance function fitting, especially in the case of sparse GNSS/leveling geoid data. Therefore LOO validation may be helpful in describing how the a priori noise parameter may affect LSC result and a posteriori error.
12
Content available Analysis of height determination using the ASG-EUPOS NAWGEO service
Dawidowicz K.
Technical Sciences / University of Warmia and Mazury in Olsztyn
|
2013
|
nr 16(1)
19--39
EN
GNSS observations carried out in a network of permanent stations are a complex systems which offer post-processing as well as corrections sent in real-time and the creation of so-called virtual observations. Currently, there are several Network-based Real Time Kinematic (NRTK) services around the world. In Poland, such a system has been in operation since June 2008, known as the Polish Active Geodetic Network (ASG-EUPOS). Three real-time correction services and two postprocessing services are currently used by users. NRTK technique uses GNSS observations gathered from a network of Continuously Operating Reference Stations (CORS) in order to generate more reliable error models that can mitigate the distance dependent errors within the area covered by the CORS. This method has been developed and tested considerably by many scientists during recent years. These studies have demonstrated the high centimeter accuracy that can be achieved using NRTK technique. This study analyzed the accuracy of the height determination with NRTK measurements using ASG-EUPOS. The results obtained show that RTK ASG-EUPOS height measurements are characterized by high precision, but the normal height measurements compared to the height measurements obtained from precise leveling, probably due to some systematic errors (the mean of many measurements differs significantly from the actual value) are not so accurate. In this case, fitting NRTK results to a precise leveling network may significantly improve the results. In presented test this resulted in reducing NRTK normal height determination errors by 70 percent.
13
Content available GNSS satellite levelling using the ASG-EUPOS system services
Dawidowicz K.
Technical Sciences / University of Warmia and Mazury in Olsztyn
|
2012
|
nr 15(1)
35-48
EN
GNSS observations from a network of permanent stations are a complex system offering not only post-processing, but also corrections sent in real time and the creation of virtual observations. In Poland, such a system has been in operation since June 2008: the Polish Active Geodetic Network ASG-EUPOS. For users three services are provided for real-time corrections, and two services are offered for post-processing. In this paper, methods of normal height determination from static GPS measurements were analysed in the context of the technical capabilities of the ASG-EUPOS along with recommendations for such measurements. Particular attention is paid to the possibility of using to such calculations the Virtual Reference Stations (VRS). Studies have shown that height determination using VRS may reduce the length of observation sessions and improve accuracy compared to the results obtained from the NAWGEO or POZGEO services. In addition, because of the short vectors between the virtual station and measured points, accuracy is not dependent on the type of used receiver (L1 or L1/L2).
PL
Obserwacje GNSS realizowane na sieciach stacji permanentnych są obecnie złożonymi systemami oferującymi, oprócz postprocessingu, również korekty przesyłane w czasie rzeczywistym oraz tworzenie obserwacji wirtualnych. W Polsce systemem takim jest uruchomiona w czerwcu 2008 roku polska aktywna sieć geodezyjna ASG EUPOS. Dla użytkowników przeznaczono trzy serwisy udostępniania poprawek w czasie rzeczywistym oraz dwa serwisy dla postprocessingu. W pracy przeanalizowano sposoby wyznaczenia wysokości z pomiarów statycznych GPS w kontekście możliwości technicznych systemu ASG-EUPOS oraz niektórych zaleceń do takich pomiarów. Szczególną uwagę zwrócono na możliwość wykorzystania do takich wyznaczeń obserwacji z Wirtualnych Stacji Referencyjnych (VRS - Virtual Reference Station). Przeprowadzone analizy wykazały, że procedura wyznaczenia wysokości punktów z wykorzystaniem VRS może pozwolić na znaczne skrócenie długości sesji obserwacyjnej oraz poprawę dokładności w stosunku do wyników uzyskanych z serwisu NAWGEO czy POZGEO. Ze względu na krótkie wektory między stacją wirtualną a wyznaczanymi punktami dokładność ta nie jest uwarunkowana wykorzystanym w czasie pomiaru typem odbiornika (L1 bądź L1/L2).
14
Content available Geoid in the area of Poland in the author's investigations
Łyszkowicz A.
Technical Sciences / University of Warmia and Mazury in Olsztyn
|
2012
|
nr 15(1)
49-64
EN
The present paper describes the results of the author's work related to the geoid determination in the area of Poland. Beginning from the geoid model geoid92 worked out in 1992, various geoid models calculated from various data sets, using various methods, are presented. Additionally, the evaluation of the accuracy of the determined geoid models is given. Next, the necessity of the fitting of computed geoid models to the national vertical reference system and the evaluation of the accuracy of the functionals N, Δg, ξ, η of the gravity field calculated from the various geopotential models are presented. It results from the presented investigations, that at present the accuracy of gravimetric geoid/quasigeoid models is ± 1.4 cm and accuracy of geoid computed from geopotential model EGM08 is ± 2.4 cm. It is stated additionally that accuracy of gravity anomalies computed from the EGM08 model is ± 25 µm s-2 , while accuracy of the deflections of the vertical ξ and η is from ± 0.6'' to ± 0.7''.
PL
W pracy przedstawiono wyniki badań dotyczących przebiegu geoidy na obszarze Polski. Poczynając od modelu geoid92, opracowanego w 1992 roku, w artykule przestawiono kolejne modele geoidy liczone z różnych danych i różnymi metodami wraz z ich charakterystyką dokładnościową. Uzasadniono konieczność dopasowania wyliczonych modeli geoidy do krajowego układu wysokościowego oraz podano dokładności charakterystyk pola siły ciężkości N, Δg, ξ, η obliczanych z kolejnych modeli geopotencjału. Z wyników badań wynika, że obecnie dokładność grawimetrycznych modeli geoidy/quasi-geoidy wynosi ± 1,4 cm, a dokładność geoidy wyliczonej z modelu geopotencjału EGM08 ± 2,4 cm. Dodatkowo stwierdzono, że dokładność anomalii grawimetrycznych wyliczonych z modelu EGM08 wynosi ± 25 µm s-2, a dokładność składowych odchyleń pionu ξ i η od ± 0.6'' do ± 0.7''.
15
Content available remote Aktywnie i wirtualnie z geoidą
Pażus R.
Geodeta : magazyn geoinformacyjny
|
2011
|
nr 6
8-13
16
Content available remote On integral approach to regional gravity field modelling from satellite gradiometric data
Eshagh M.
Acta Geophysica
|
2011
|
Vol. 59, no. 1
29-54
EN
Solution of the gradiometric boundary value problems leads to three integral formulas. If we are satisfied with obtaining a smooth solution for the Earth’s gravity field, we can use the formulas in regional gravity field modelling. In such a case, satellite gradiometric data are integrated on a sphere at satellite level and continued downward to the disturbing potential (geoid) at sea level simultaneously. This paper investigates the gravity field modelling from a full tensor of gravity at satellite level. It studies the truncation bias of the integrals as well as the filtering of noise of data. Numerical studies show that by integrating Tzz with 1 mE noise and in a cap size of 7°, the geoid can be recovered with an error of 12 cm after the filtering process. Similarly, the errors of the recovered geoids from Txz,yz and Txx-yy, 2xy are 13 and 21 cm, respectively.
17
Content available remote Quasigeoid for the area of Poland computed by least squares collocation
Łyszkowicz A.
Technical Sciences / University of Warmia and Mazury in Olsztyn
|
2010
|
nr 13
147-164
EN
The quasigeoid models recently computed in Poland e.g. (Łyszkowicz, Kryński 2006) and abroad e.g. (Al Marzooqi et al. 2005) were computed from Stokes'a integral by Fast Fourier Technique (FFT). At present because of significant capability of personal computers and proper strategy of computation more often for geoid/quasigeoid computation the least squares collocation is used. In the present paper is described the first quasigeoid computation by least collocation for the area of Poland. The quasigeoid model was computed in two version, namely from the gravity data only and from the gravity and vertical deflections data simultaneously. The differences between these two versions are small and do not exceed 1-2 mm. In order to evaluate the advantages coming from the collocation the third pure gravimetric model using Stokes'a integral was computed and compared with the gravimetric model computed by collocation. The differences between these versions are significant and at the level of 20 cm, beside the collocation model is better.
PL
Wszystkie ostatnio liczone grawimetryczne modele quasi-geoidy w Polsce (np. Łyszkowicz, Kryński 2006) i na świecie (np. Al Marzooqi et al. 2005) były liczone na podstawie całki Stokesa, do której oszacowania wykorzystywano szybką transformatę Fouriera (FFT). Obecnie ze względu na znaczne możliwości komputerów oraz odpowiednio opracowaną strategię obliczeniową coraz częściej do wyznaczenia przebiegu geoidy/quasi-geoidy wykorzystuje się metodę kolokacji. W pracy przedstawiono pierwsze w Polsce wyznaczenie przebiegu quasi-geoidy metodą kolokacji. Model quasi-geoidy wyznaczono w dwóch wariantach, a mianowicie tylko z danych grawimetrycznych, a następnie łącznie z danych grawimetrycznych i astro-geodezyjnych odchyleń pionu. Różnice między tymi dwoma wariantami są minimalne i wynoszą 1-2 mm. W celu oceny korzyści wynikających z metody kolokacji grawimetryczną quasi-geoidę policzono również metodą FFT i porównano z quasi-geoidą obliczoną metodą kolokacji. Z przeprowadzonego porównania wynika, że rozbieżność między modelami jest rzędu 20 cm, z tym że quasi-geoida kolokacyjna jest lepsza.
18
Content available remote EGM08 Globalna supergeoida
Łyszkowicz A.
Geodeta : magazyn geoinformacyjny
|
2009
|
nr 6
12-14
19
Content available remote Spherical harmonics expansion of the atmospheric gravitational potential based on exponential and power models of atmosphere
Eshagh M.
Artificial Satellites : Journal of Planetary Geodesy
|
2008
|
Vol. 43, No. 1
25--43
EN
Spherical harmonic formulation of gravitational potential of the atmosphere depends on the analytical model of the atmospheric density which is used. Exponential and power models are two well-known mathematical tools which are used in atmospheric applications. This paper presents simple formulas for the harmonic coefficients of internal and external types of the atmospheric potential based on these models which can be used in most of the gravimetric aspects. It considers the atmospheric effect on the satellite gravity gradiometry data as an example for numerical investigations. The numerical studies on these data show that the maximum atmospheric effect is about 2 mE over Fennoscandia based on both models, and their differences are less than 0.1 mE. The difference between indirect atmospheric effects reaches 2 cm and 0.02 mGal on the geoid and gravity anomaly, respectively in this region.
20
Content available remote Interpretation of general geophysical patterns in Iran based on GRACE gradient component analysis
Kiamehr R., Eshagh M., Sjöberg L. E.
Acta Geophysica
|
2008
|
Vol. 56, no. 2
440-454
EN
Only with satellites it is possible to cover the entire Earth densely with gravity field related measurements of uniform quality within a short period of time. How-ever, due to the altitude of the satellite orbits, the signals of individual local masses are strongly damped. Based on the approach of Petrovskaya and Vershkov we determine the gravity gradient tensor directly from the spherical harmonic coefficients of the recent EIGEN-GL04C combined model of the GRACE satellite mission. Satellite gradiometry can be used as a complementary tool to gravity and geoid information in interpreting the general geophysical and geodynamical features of the Earth. Due to the high altitude of the satellite, the effects of the topography and the internal masses of the Earth are strongly damped. However, the gradiometer data, which are nothing else than the second order spatial derivatives of the gravity potential, efficiently counteract signal attenuation at the low and medium frequencies. In this article we review the procedure for estimating the gravity gradient components directly from spherical harmonics coefficients. Then we apply this method as a case study for the interpretation of possible geophysical or geodynamical patterns in Iran. We found strong correlations between the cross-components of the gravity gradient tensor and the components of the deflection of vertical, and we show that this result agrees with theory. Also, strong correlations of the gravity anomaly, geoid model and a digital elevation model were found with the diagonal elements of the gradient tensor.
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