Comparison and Assessment of Three ITRS Realizations

A terrestrial reference frame (TRF) is derived based on historical geodetic data and is normally updated every 5–6 years. The three most recent International Terrestrial Reference System (ITRS) realizations, ITRF2014, DTRF2014, and JTRF2014, were determined with different strategies, which has resulted in different signals in the reference frame parameters. In this paper, we used the continuous site position time series of International GNSS Service (IGS) from 1995 to 2020 as a benchmark to investigate the characteristics of the three frames. In the comparison, the ITRS realizations were divided into the determination and prediction sections, where the site coordinates of the TRFs were extrapolated in the prediction period. The results indicated that the orientation and scale parameters of the ITRF2014, and the IGS solutions showed excellent agreement during the determination period of ITRF2014, while, during the prediction period, the orientation parameter diverged from IGS with rates of 11.9, 5.5, and 8.4 as/yr, and the scale degraded with a rate of −0.038 ppb/yr. The consistency of the origin parameters between the DTRF2014 and the IGS solutions during the two periods changed from 0.07, 0.11, and −0.15 mm/yr to −0.17, −0.18, and −0.12 mm/yr; the consistency of orientation parameters from −3.6, −1.9, and 2.9 as/yr to 15.9, −2.3, and 13.2 as/yr; and the consistency of scale from 0.007 to −0.005 ppb/yr. In the comparison between the JTRF2014 and IGS solutions, annual signals in the origin differences were 1.5, 3.0, and 2.4 mm in the X, Y, and Z components, respectively, and the temporal variation trends in different periods disagreed with their long-term trends. Obvious trend switches in the rotation parameters were also observable, and the complex temporal variation characteristics of the scale offsets may be related to the scale definition strategy applied in different TRFs.

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The Estimation and Prediction of Geocenter Motion Based on GNSS Weekly Solutions

10.5194/egusphere-egu2020-2504 ◽

2020 ◽

Author(s):

Chunmei Zhao ◽

Lingna Qiao ◽

Tianming Ma

Keyword(s):

Reference Frame ◽

Prediction Accuracy ◽

Center Of Mass ◽

Science Research ◽

Terrestrial Reference Frame ◽

Small Contribution ◽

The Earth ◽

Term Prediction ◽

Geocenter Motion

The development of satellite space geodesy technology makes the establishment of global terrestrial reference frame based on the Earth&#8217;s center of mass become reality. Precise and stable terrestrial reference frame is the foundation of the Earth science research, while determination and analysis of the position of the Earth's center of mass and its change is an important part to build high precision terrestrial reference frame. Based on GNSS weekly solutions provided by IGS, the geocenter motion (GM) time series between 2007 and 2017 are obtained by means of net translation method. Then the amplitude of the annual term of geocentric motion is 2.27mm, 1.84mm and 2.13mm in the direction of X, Y and Z respectively, and the amplitude of the half-year term is 0.1mm, 0.20mm and 0.15mm respectively. In addition, some other inter-annual changes with relatively small contribution rate are found. Finally, in order to get reliable GM prediction ,two kinds of methods are used, which are ARMA and SSA+ARMA. In the short-term prediction, the accuracy of the two methods is the same, both can reach the millimeter level of prediction accuracy, but SSA+ARMA is more stable. SSA+ARMA algorithm is much better in the medium and long-term scale, and it can provide 1mm medium term prediction accuracy and 1.5mm long term prediction accuracy.

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The Combined Solution C04 for Earth Orientation Parameters Consistent with International Terrestrial Reference Frame 2005

Geodetic Reference Frames - International Association of Geodesy Symposia ◽

10.1007/978-3-642-00860-3_41 ◽

2009 ◽

pp. 265-270 ◽

Cited By ~ 97

Author(s):

Christian Bizouard ◽

Daniel Gambis

Keyword(s):

Reference Frame ◽

Terrestrial Reference Frame ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

International Terrestrial Reference Frame ◽

Combined Solution ◽

Orientation Parameters

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Unconstrained Estimation of VLBI Global Observing System Station Coordinates

Advances in Geosciences ◽

10.5194/adgeo-55-23-2021 ◽

2021 ◽

Vol 55 ◽

pp. 23-31

Author(s):

Markus Mikschi ◽

Johannes Böhm ◽

Matthias Schartner

Keyword(s):

Reference Frame ◽

Terrestrial Reference Frame ◽

Baseline Length ◽

Radio Telescopes ◽

Earth Orientation Parameters ◽

The Earth ◽

Station Coordinates ◽

International Vlbi Service ◽

Orientation Parameters

Abstract. The International VLBI Service for Geodesy and Astrometry (IVS) is currently setting up a network of smaller and thus faster radio telescopes observing at broader bandwidths for improved determination of geodetic parameters. However, this new VLBI Global Observing System (VGOS) network is not yet strongly linked to the legacy S/X network and the International Terrestrial Reference Frame (ITRF) as only station WESTFORD has ITRF2014 coordinates. In this work, we calculated VGOS station coordinates based on publicly available VGOS sessions until the end of 2019 while defining the geodetic datum by fixing the Earth orientation parameters and the coordinates of the WESTFORD station in an unconstrained adjustment. This set of new coordinates allows the determination of geodetic parameters from the analysis of VGOS sessions, which would otherwise not be possible. As it is the concept of VGOS to use smaller, faster slewing antennas in order to increase the number of observations, shorter estimation intervals for the zenith wet delays and the tropospheric gradients along with different relative constraints were tested and the best performing parametrization, judged by the baseline length repeatability, was used for the estimation of the VGOS station coordinates.

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A preliminary assessment of the accuracy of the VGOS geodetic products: implications for the terrestrial reference frame and Earth orientation parameters

10.5194/egusphere-egu21-13032 ◽

2021 ◽

Author(s):

Dhiman Mondal ◽

Pedro Elosegui ◽

John Barrett ◽

Brian Corey ◽

Arthur Niell ◽

...

Keyword(s):

Reference Frame ◽

Mixed Mode ◽

Daily Basis ◽

Terrestrial Reference Frame ◽

Preliminary Assessment ◽

Earth Orientation Parameters ◽

Vlbi Observations ◽

International Vlbi Service ◽

Single Baseline ◽

Orientation Parameters

The next-generation VLBI system called VGOS (VLBI Global Observing System) has been designed and built as a significant improvement over the legacy geodetic VLBI system to meet the accuracy and stability goals set by the Global Geodetic Observing System (GGOS). Improved geodetic products are expected as the VGOS technique transitions from demonstration to operational status, which is underway. Since 2019, a network of nine VGOS stations has been observing bi-weekly under the auspices of the International VLBI Service for Geodesy and Astrometry (IVS) to generate standard geodetic products. These products, together with the mixed-mode VLBI observations that tie the VGOS and legacy networks together will be contributions to the next realization of the International Terrestrial Reference Frame (ITRF2020). Moreover, since 2020 a subset of 2 to 4 VGOS stations has also been observing in a VLBI Intensive-like mode to assess the feasibility of Earth rotation (UT1) estimation using VGOS. Intensives are daily legacy VLBI observations that are run on a daily basis using a single baseline between Kokee Park Geophysical Observatory, Hawaii, and Wettzell Observatory, Germany, made with the goal of near-real-time monitoring of UT1. In this presentation, we will describe the VGOS observations, correlation, post-processing, and preliminary geodetic results, including UT1. We will also compare the VGOS estimates to estimates from legacy VLBI, including estimates from mixed-mode observations, to explore the precision and accuracy of the VGOS products.

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GPS z-PCO and GNSS-based scale determined by integrated processing with LEOs and Galileo

10.5194/egusphere-egu21-4798 ◽

2021 ◽

Author(s):

Wen Huang ◽

Benjamin Männel ◽

Andreas Brack ◽

Harald Schuh

Keyword(s):

Reference Frame ◽

A Priori ◽

Terrestrial Reference Frame ◽

International Gnss Service ◽

Satellite Transmitter ◽

Ground Station ◽

Station Coordinates ◽

Integrated Processing ◽

Current Constellation ◽

The Impact

The Global Positioning System (GPS) satellite transmitter antenna phase center offsets (PCOs) in z-direction and the scale of the terrestrial reference frame are highly correlated when neither of them is constrained to an a priori value in a least-squares adjustment. The commonly used PCO values offered by the International GNSS Service (IGS) are estimated in a global adjustment by constraining the ground station coordinates to the current International Terrestrial Reference Frame (ITRF). As the scale of the ITRF is determined by other techniques, the estimated GPS z-PCOs are not independent. Consequently, the z-PCOs transfer the scale to any subsequent GNSS solution. To get a GNSS-based scale that can contribute to a future ITRF realization, two methods are proposed to determine scale-independent GPS z-PCOs. One method is based on the gravitational constraint on Low Earth Orbiters (LEOs) in an integrated processing of the GPS satellites and LEOs. The correlation coefficient between the GPS PCO-z and the scale is reduced from 0.85 to 0.3 by supplementing a 54-ground-station network with seven LEOs. The impact of individual LEOs on the estimation is discussed by including different subsets of the LEOs. The accuracy of the z-PCOs of the LEOs is very important for the accuracy of the solution. In another method, the GPS z-PCOs and the scale are determined in a GPS+Galileo processing where the PCOs of Galileo are fixed to the values calibrated on ground from the released metadata. The correlation between the GPS PCO-z and the scale is reduced to 0.13 by including the current constellation of Galileo with 24 satellites. We use the whole constellation of Galileo and the three LEOs of the Swarm mission to perform a direct comparison and cross-check of the two methods. The two methods provide mean GPS z-PCO corrections of -186&#177;25 mm and -221&#177;37 mm with respect to the IGS values, and +1.55&#177;0.22 ppb (part per billion) and +1.72&#177;0.31 ppb in the terrestrial scale with respect to the IGS14 reference frame. The results of both methods agree with each other with only small differences. Due to the larger number of Galileo observations, the Galileo-PCO-fixed method leads to more precise and stable results. In the joint processing of GPS+Galileo+Swarm in which both methods are applied, the constraint on Galileo dominates the results. We also discuss how fixing either the Galileo transmitter antenna z-PCO or the Swarm receiver antenna z-PCOs in the GPS+Galileo+Swarm processing propagates to the respective freely estimated z-PCOs of Swarm or Galileo.

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AVALIAÇÃO DO DESEMPENHO DOS SISTEMAS GPS E GLONASS NO POSICIONAMENTO POR PONTO PRECISO, COMBINADOS E INDIVIDUALMENTE.

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702016000200015 ◽

2016 ◽

Vol 22 (2) ◽

pp. 265-281 ◽

Cited By ~ 2

Author(s):

Bruno Guimarães Ventorim ◽

William Rodrigo Dal Poz

Keyword(s):

Reference Frame ◽

Global Positioning System ◽

Terrestrial Reference Frame ◽

Positioning System ◽

International Gnss Service ◽

International Terrestrial Reference Frame ◽

Global Positioning ◽

Quality Check

Este trabalho visa avaliar o desempenho dos sistemas GLONASS (Global'naya Navigatsionnay Sputnikovaya Sistema), GPS (Global Positioning System) e o uso combinado de ambos sistemas em diferentes latitudes, utilizando o serviço de Posicionamento por Ponto Preciso CSRS-PPP. Para isso foram selecionadas 16 estações da rede IGS (International GNSS Service), das quais foram utilizados os dados GNSS no formato RINEX do mês de agosto de 2014 e editados no TEQC (Translation, Editing, and Quality Check), obtendo arquivos com intervalos de 30 e 45 minutos, contendo apenas dados GPS, dados GLONASS e dados dos dois sistemas. As coordenadas estimadas no CSRS-PPP foram comparadas com as coordenadas de referência obtidas no sítio do ITRF (International Terrestrial Reference Frame), possibilitando o cálculo da acurácia do PPP com uso de dados GPS e GLONASS, separadamente e em conjunto. Após o cálculo das acurácias para cada dia de agosto, outliers foram detectados e eliminados utilizando o método boxplot com o uso do programa R. Verificou-se que o uso combinado do GPS e GLONASS, para todos as estações, proporcionou resultados mais acurados. Além disso, pode-se destacar a potencialidade do GLONASS, que apresentou desempenho superior ao do GPS na maioria das estações.

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Verification of the Polish Geodetic Reference Frame by Means of a New Solution Based on Permanent GNSS Data from the Years 2011-2014

Reports on Geodesy and Geoinformatics ◽

10.1515/rgg-2016-0027 ◽

2016 ◽

Vol 102 (1) ◽

pp. 52-66 ◽

Cited By ~ 1

Author(s):

T. Liwosz ◽

M. Ryczywolski

Keyword(s):

Reference Frame ◽

Primary Network ◽

Position Time Series ◽

Gnss Network ◽

Gnss Data ◽

Geodetic Reference Frame ◽

Minimum Constraints ◽

Data Length ◽

Good Agreement

Abstract The new solution for the Polish geodetic primary GNSS network was created to verify the currently used reference frame (PL-ETRF2000). The new solution is based on more GNSS data (more daily observation sessions included, a longer data timespan, GLONASS observations added) which were processed in a newer reference frame (IGb08) according to up-to-date methodology and using the latest version of Bernese GNSS Software. The new long-term solution (spanning 3.7 years) was aligned to the IGb08 reference frame using a minimum constraints approach. We categorized Polish reference stations into two categories according to their data length. We obtained good agreement of the new solution with the PL-ETRF2000: for most stations position differences did not exceed 5 mm in horizontal, and 10 mm in vertical components. However, for 30 stations we observed discontinuities in position time series, mostly due to GNSS equipment changes, which occured after the introduction of PL-ETRF2000. Position changes due to the discontinuities reached 9.1 mm in horizontal components, and 26.9 mm in vertical components. The new solution takes into account position discontinuities, and in addition also includes six new stations which were installed after the introduction of the PL-ETRF2000. Therefore, we propose to update the currently-used reference frame for the Polish geodetic primary network (PL-ETRF2000) with the new solution. The new solution was also accepted by the EUREF Technical Working Group as a class A solution (highest accuracy) according to EUREF standards.

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Contribution of the Vienna Center for VLBI to ITRF2020

10.5194/egusphere-egu21-1088 ◽

2021 ◽

Author(s):

Hana Krásná ◽

David Mayer ◽

Sigrid Böhm

Keyword(s):

Reference Frame ◽

Terrestrial Reference Frame ◽

Normal Equation ◽

Earth Orientation Parameters ◽

International Vlbi Service ◽

Analysis Center ◽

International Terrestrial Reference System ◽

Terrestrial Reference System ◽

The Impact ◽

Orientation Parameters

The next realization of the International Terrestrial Reference System, the ITRF2020, is planned to be released in 2021. Our joint VLBI Analysis Center VIE which runs between TU Wien and BEV is one of eleven IVS (International VLBI Service for Geodesy and Astrometry) analysis centres which provide VLBI input to the ITRF2020. The SINEX files submitted to the IVS Combination Center are produced with the Vienna VLBI and Satellite Software VieVS and contain unconstrained normal equation systems for station position, source coordinates and Earth orientation parameters. In this presentation, we document the included sessions and stations in our submission and introduce the Vienna terrestrial reference frame based on our contribution to the ITRF2020. In particular, we highlight special settings in the Vienna solution and assess the impact on the terrestrial reference frame.

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