Estimation and Analysis of the Observable-Specific Code Biases Estimated Using Multi-GNSS Observations and Global Ionospheric Maps

Observable-specific bias (OSB) parameterization allows observation biases belonging to various signal types to be flexibly addressed in the estimation of ionosphere and global navigation satellite system (GNSS) clock products. In this contribution, multi-GNSS OSBs are generated by two different methods. With regard to the first method, geometry-free (GF) linear combinations of the pseudorange and carrier-phase observations of a global multi-GNSS receiver network are formed for the extraction of OSB observables, and global ionospheric maps (GIMs) are employed to correct ionospheric path delays. Concerning the second method, satellite and receiver OSBs are converted directly from external differential code bias (DCB) products. Two assumptions are employed in the two methods to distinguish satellite- and receiver-specific OSB parameters. The first assumption is a zero-mean condition for each satellite OSB type and GNSS signal. The second assumption involves ionosphere-free (IF) linear combination signal constraints for satellites and receivers between two signals, which are compatible with the International GNSS Service (IGS) clock product. Agreement between the multi-GNSS satellite OSBs estimated by the two methods and those from the Chinese Academy of Sciences (CAS) is shown at levels of 0.15 ns and 0.1 ns, respectively. The results from observations spanning 6 months show that the multi-GNSS OSB estimates for signals in the same frequency bands may have very similar code bias characteristics, and the receiver OSB estimates present larger standard deviations (STDs) than the satellite OSB estimates. Additionally, the variations in the receiver OSB estimates are shown to be related to the types of receivers and antennas and the firmware version. The results also indicate that the root mean square (RMS) of the differences between the OSBs estimated based on the CAS- and German Aerospace Center (DLR)-provided DCB products are 0.32 ns for the global positioning system (GPS), 0.45 ns for the BeiDou navigation satellite system (BDS), 0.39 ns for GLONASS and 0.22 ns for Galileo.

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Epoch-by-epoch estimation and analysis of BDS receiver differential code biases with the additional BDS-3 observations

10.5194/angeo-2020-37 ◽

2020 ◽

Author(s):

Qisheng Wang ◽

Shuanggen Jin ◽

Youjian Hu

Keyword(s):

Satellite System ◽

Global Navigation Satellite Systems ◽

Navigation Satellite ◽

Satellite Systems ◽

Code Bias ◽

Space Environments ◽

Receiver Dcb ◽

German Aerospace ◽

Global Navigation Satellite ◽

Academy Of Sciences

Abstract. The differential code bias (DCB) of global navigation satellite systems (GNSS) is an important error source in ionospheric modeling, which was generally estimated as constants every day. However, the receiver DCB may be changing due to the varying space environments and temperatures. In this paper, the receiver DCB of BeiDou Navigation Satellite System (BDS) is estimated as the changing parameter within one day with epoch-by-epoch. The BDS receiver DCBs are analyzed from 30 days of multi-GNSS experiment observations. The comparison of estimated receiver DCB of BDS with the DCB provided by German Aerospace Center (DLR) and Chinese Academy of Sciences (CAS) shows a good agreement. The root mean square (RMS) values of receiver DCB are 0.43 and 0.80 ns with respect to DLR and CAS, respectively. In terms of the intra-day variability of receiver DCB, most of the receiver DCBs show relative stability within one day with the intra-day standard deviation (STD) of less than 1 ns. However, larger fluctuations with more than 2 ns of intra-day receiver DCB are found. Besides, the intra-day stability of receiver DCB calculated by the third-generation BDS (BDS-3) and the second-generation BDS (BDS-2) observations is compared. The result shows that the intra-day stability of BDS-3 receiver DCB is better than that of BDS-2 receiver DCB.

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Epoch-by-epoch estimation and analysis of BeiDou Navigation Satellite System (BDS) receiver differential code biases with the additional BDS-3 observations

Annales Geophysicae ◽

10.5194/angeo-38-1115-2020 ◽

2020 ◽

Vol 38 (5) ◽

pp. 1115-1122

Author(s):

Qisheng Wang ◽

Shuanggen Jin ◽

Youjian Hu

Keyword(s):

Satellite System ◽

Navigation Satellite ◽

Beidou Navigation Satellite System ◽

Code Bias ◽

Receiver Dcb ◽

German Aerospace ◽

Global Navigation Satellite ◽

Academy Of Sciences ◽

Better Than ◽

Good Agreement

Abstract. The differential code bias (DCB) of the Global Navigation Satellite System (GNSS) is an important error source in ionospheric modeling, which was generally estimated as constants every day. However, the receiver DCB may be changing due to the varying spatial environments and temperatures. In this paper, a method based on the global ionospheric map (GIM) of the Center for Orbit Determination in Europe (CODE) is presented to estimate the BeiDou Navigation Satellite System (BDS) receiver DCB with epoch-by-epoch estimates. The BDS receiver DCBs are analyzed from 30 d of Multi-GNSS Experiment observations. The comparison of estimated receiver DCB of BDS with the DCB provided by the German Aerospace Center (DLR) and the Chinese Academy of Sciences (CAS) shows a good agreement. The root-mean-square (rms) values of receiver DCB are 0.43 and 0.80 ns with respect to the DLR and CAS estimates, respectively. In terms of the intraday variability of receiver DCB, most of the receiver DCBs show relative stability within 1 d with the intraday standard deviation (SD) of less than 1 ns. However, larger fluctuations with more than 2 ns of intraday receiver DCB are found. Besides, the intraday stability of receiver DCB calculated by the third-generation BDS (BDS-3) and the second-generation BDS (BDS-2) observations is compared. The result shows that the intraday stability of BDS-3 receiver DCB is better than that of BDS-2 receiver DCB.

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Estimation and Analysis of BDS-3 Differential Code Biases from MGEX Observations

Remote Sensing ◽

10.3390/rs12010068 ◽

2019 ◽

Vol 12 (1) ◽

pp. 68 ◽

Cited By ~ 7

Author(s):

Wang ◽

Jin ◽

Yuan ◽

Hu ◽

Chen ◽

...

Keyword(s):

Satellite System ◽

Mean Value ◽

Systematic Bias ◽

Navigation Satellite ◽

Code Bias ◽

Receiver Dcb ◽

The Stability ◽

Global Navigation Satellite ◽

Academy Of Sciences ◽

Good Agreement

The third generation of China’s BeiDou Navigation Satellite System (BDS-3) began to provide global services on 27 December, 2018. Differential code bias (DCB) is one of the errors in precise BDS positioning and ionospheric modeling, but the impacts on BDS-2 satellites and receiver DCB are unknown after joining BDS-3 observations. In this paper, the BDS-3 DCBs are estimated and analyzed using the Multi-Global Navigation Satellite System (GNSS) Experiment (MGEX) observations during the period of day of year (DOY) 002–031, 2019. The results indicate that the estimated BDS-3 DCBs have a good agreement with the products provided by the Chinese Academy of Sciences (CAS) and Deutsche Zentrum für Luft- und Raumfahrt (DLR). The differences between our results and the other two products are within ±0.2 ns, with Standard Deviations (STDs) of mostly less than 0.2 ns. Furthermore, the effects on satellite and receiver DCB after adding BDS-3 observations are analyzed by BDS-2 + BDS-3 and BDS-2-only solutions. For BDS-2 satellite DCB, the values of effect are close to 0, and the effect on stability of DCB is very small. In terms of receiver DCB, the value of effect on each station is related to the receiver type, but their mean value is also close to 0, and the stability of receiver DCB is better when BDS-3 observations are added. Therefore, there is no evident systematic bias between BDS-2 and BDS-2 + BDS-3 DCB.

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Centro de Análise Sirgas - IBGE: novas estratégias de processamento e combinação, e a influência da mudança do referencial global nos resultados

Boletim de Ciências Geodésicas ◽

10.1590/s1982-21702012000100004 ◽

2012 ◽

Vol 18 (1) ◽

pp. 63-85

Author(s):

Sonia Maria Alves Costa ◽

Alberto Luis Da Silva ◽

Marco Aurélio De Almeida Lima ◽

Newton José De Moura Júnior

Keyword(s):

Global Navigation Satellite System ◽

Satellite System ◽

Navigation Satellite ◽

International Gnss Service ◽

Global Navigation ◽

Global Navigation Satellite

Atualmente, o SIRGAS (Sistema de Referência Geocêntrico para as Américas) é realizado por uma rede GNSS (Global Navigation Satellite System) permanente denominada SIRGAS-CON, com cerca de 240 estações em funcionamento permanente, distribuídas na América do Sul, Central e Caribe. Os Centros de Análise SIRGAS foram estabelecidos com a finalidade de determinar sistematicamente as coordenadas das estações SIRGAS-CON, seguindo padrões estabelecidos internacionalmente, a fim de apoiar a manutenção do sistema e as atividades do Grupo de Trabalho SIRGAS-GT I (Sistema de Referência). Desde agosto de 2008 a Coordenação de Geodésia do Instituto Brasileiro de Geografia e Estatística-IBGE assumiu oficialmente as atividades de um Centro de Análise. Este é um trabalho cuja dedicação é crescente uma vez que o número de estações no continente Sul Americano vem aumentando rapidamente nos últimos anos. Desta atividade diária são geradas dentre outros resultados, as séries temporais das coordenadas de cada estação, possibilitando assim a determinação dos deslocamentos das estações em função da movimentação da crosta terrestre, os movimentos locais como subsidência e/ou soerguimento crustal, causados por fenômenos naturais, como por exemplo, terremotos, além de efeitos sazonais causados por fatores diversos. Paralelamente a atividade de processamento dos dados GNSS, o IBGE também realiza semanalmente a combinação das soluções semanais dos nove Centros de Processamento SIRGAS. Esta combinação tem por objetivo comparar os resultados com os obtidos pelo DGFI (Deutsches Geodätisches Forschungsinstitut), o qual disponibiliza a solução final semanal da rede SIRGAS-CON. Por se tratar de resultados precisos, a mudança em alguma informação no processamento pode acarretar alterações nas coordenadas determinadas e, conseqüentemente, descontinuidades nas séries temporais de cada estação. Recentemente, em 17 de abril de 2011 (semana GPS 1632), as órbitas (finais e rápidas), as correções dos relógios dos satélites e o modelo de calibração das antenas disponibilizado pelo International GNSS Service - IGS, passaram a estar referidos à nova realização do IGS, denominada IGS08. Conseqüentemente, a partir dessa data, os processamentos GPS que utilizam os produtos IGS terão seus resultados referidos a este novo sistema de referência, o que poderá acarretar descontinuidades nas coordenadas. O objetivo desse trabalho é apresentar a estratégia de processamento atualmente em operação, bem com uma nova estratégia visando à melhoria dos resultados. Outro objetivo é apresentar alguns resultados do processamento e combinação semanal realizados pelo IBGE, bem como esclarecer as alterações ocorridas com a adoção da nova versão da Rede de Referência Global para soluções GNSS, o IGS08 e uma análise preliminar da conseqüência desta mudança.

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A Comparative Study for Performance Analysis of Kinematic Multi-Constellation GNSS PPP in Dynamic Environment

Journal of Marine Science and Engineering ◽

10.3390/jmse8070514 ◽

2020 ◽

Vol 8 (7) ◽

pp. 514

Author(s):

Serdar Erol

Keyword(s):

Global Navigation Satellite System ◽

Test Procedure ◽

Dynamic Environment ◽

Satellite System ◽

Research Centre ◽

Navigation Satellite ◽

Post Processing ◽

International Gnss Service ◽

Global Navigation ◽

Global Navigation Satellite

This case study aims to investigate the effect of different Multi-GNSS EXperiment (MGEX) precise products provided by International GNSS Service (IGS) Analysis Centers (ACs) on post-processing kinematic Precise Point Positioning (PPP) accuracy performance with different satellite system combinations in a dynamic environment. Within this frame, a test was carried out in a lake and kinematic data were collected over 6 h at 1 Hz rate from the available Global Navigation Satellite System (GNSS) constellations with the geodetic-grade receiver fixed on a marine vehicle for bathymetric mapping. PPP-derived coordinates were determined by a commercial GNSS post-processing software with different processing approaches as GPS (Global Positioning System)-only, GPS+GLObal’naya NAvigatsionnaya Sputnikovaya Sistema (GLONASS), GPS+GLONASS+European Global Navigation Satellite System (Galileo), GPS+GLONASS+Chinese Global Navigation Satellite System (BeiDou), and GPS+GLONASS+Galileo+BeiDou. The PPP coordinates were then compared to the reference coordinates obtained from the post-processed carrier phase-based differential kinematic solutions. In general, the results showed that the kinematic multi-constellation GNSS PPP technique could provide positioning accuracy from cm to decimeter level as depending on the collected data constellations and used precise products in the processing. Among all solutions, the GPS+GLONASS+Galileo+BeiDou combination with German Research Centre for Geosciences (GFZ)’s precise products presented the best multi-GNSS PPP performance, rather than the other combinations and quad-constellation alternatives using different precise products. In this study, the test procedure and the obtained results are given in detail.

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Potencialidades do PPP no Software Bernese com Compatibilizações de Sistemas Geodésicos de Referência e de Tempo

Revista Brasileira de Cartografia ◽

10.14393/rbcv71n3-47483 ◽

2019 ◽

Vol 71 (3) ◽

pp. 726-755

Author(s):

Franciele Lúcia Silva Braga ◽

William Rodrigo Dal Poz

Keyword(s):

Global Navigation Satellite System ◽

Satellite System ◽

Navigation Satellite ◽

International Gnss Service ◽

Global Navigation ◽

Global Navigation Satellite

O Software Bernese GNSS (BSW) é um conjunto de pacotes de processamento de observáveis GNSS (Global Navigation Satellite System) de alto desempenho, que proporciona estimativas com alta acurácia, e flexibilidade em suas aplicações. Uma destas funcionalidades é a automatização de scripts que realizam o Posicionamento por Ponto Preciso (PPP). O objetivo deste trabalho é analisar as potencialidades do PPP no BSW. Para alcançar esse propósito foram estimadas as coordenadas de 90 estações da RBMC (Rede Brasileira de Monitoramento Contínuo dos Sistemas GNSS) no BSW e no serviço IBGE-PPP online, referenciadas a atual realização do International GNSS Service, o IGS14, na época dos dados. As coordenadas estimadas foram comparadas com as coordenadas de referência das estações (SIRGAS2000, época 2000,40), de três formas distintas: 1. Referenciais e épocas incompatíveis; 2. Compatibilização apenas dos referenciais; e 3. Referenciais e épocas compatíveis. As acurácias das coordenadas reduziram no processo de compatibilização de referenciais. Como esperado, o fator predominante na alteração das coordenadas planimétricas se refere à sua evolução temporal. Ademais, as acurácias planimétricas e altimétricas apresentaram estatísticas descritivas similares ao nível do milímetro, evidenciando a potencialidade do BSW no PPP.

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Accuracy Analysis of GNSS Hourly Ultra-Rapid Orbit and Clock Products from SHAO AC of iGMAS

Remote Sensing ◽

10.3390/rs13051022 ◽

2021 ◽

Vol 13 (5) ◽

pp. 1022

Author(s):

Qinming Chen ◽

Shuli Song ◽

Weili Zhou

Keyword(s):

Real Time ◽

Satellite System ◽

High Accuracy ◽

Observation Data ◽

Navigation Satellite ◽

International Gnss Service ◽

Observation Session ◽

New Strategy ◽

Analysis Center ◽

Global Navigation Satellite

With the development of the global navigation satellite system(GNSS), the hourly ultra-rapid products of GNSS are attracting more attention due to their low latency and high accuracy. A new strategy and method was applied by the Shanghai Astronomical Observatory (SHAO) Analysis Center (AC) of the international GNSS Monitoring and Assessment Service (iGMAS) for generating 6-hourly and 1-hourly GNSS products, which mainly include the American Global Positioning System (GPS), the Russian Global’naya Navigatsionnaya Sputnikova Sistema (GLONASS), the European Union’s Galileo, and the Chinese BeiDou navigation satellite system (BDS). The 6-hourly and 1-hourly GNSS orbit and clock ultra-rapid products included a 24-h observation session which is determined by 24-h observation data from global tracking stations, and a 24-h prediction session which is predicted from the observation session. The accuracy of the 1-hourly orbit product improved about 1%, 31%, 13%, 11%, 23%, and 9% for the observation session and 18%, 43%, 45%, 34%, 53%, and 15% for the prediction session of GPS, GLONASS, Galileo, BDS Medium Earth Orbit (MEO), Inclined Geosynchronous Orbit (IGSO), and GEO orbit, when compared with reference products with high accuracy from the International GNSS service (IGS).The precision of the 1-hourly clock products can also be seen better than the 6-hourly clock products. The accuracy and precision of the 6-hourly and 1-hourly orbit and clock verify the availability and reliability of the hourly ultra-rapid products, which can be used for real-time or near-real-time applications, and show encouraging prospects.

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Phase Center Corrections for BDS IGSO and MEO Satellites in IGb14 and IGSR3 Frame

Remote Sensing ◽

10.3390/rs13040745 ◽

2021 ◽

Vol 13 (4) ◽

pp. 745

Author(s):

Ziyang Qu ◽

Jing Guo ◽

Qile Zhao

Keyword(s):

Satellite System ◽

Navigation Satellite ◽

International Gnss Service ◽

Phase Center ◽

Reliable Estimation ◽

Station Coordinates ◽

Good Consistency ◽

Phase Center Variations ◽

Global Navigation Satellite ◽

Initial Combination

As pre-launch antenna calibrations are not available for GPS and GLONASS satellites, the high correlation between the terrestrial scale and phase center offset (PCO) prevents a reliable estimation of the terrestrial scale with GNSS (Global Navigation Satellite System) technology. Fortunately, the ground calibrated PCO values for Galileo, BeiDou navigation satellite system (BDS), and QZSS have been released, making a reliable estimation of the terrestrial scale with GNSS possible. In the third reprocess (repro3) of International GNSS Service (IGS), the terrestrial scale derived with Galileo, has been used. To evaluate the consistency of the terrestrial scale derived from the BDS-released PCOs as well as Galileo-released ones, and to incorporate BDS into IGS repro3 as well as operational legacy analysis, the phase center variations (PCV) and PCO for BDS medium earth orbit (MEO) and inclined geostationary orbit (IGSO) satellites are estimated to be consistent with GPS/GLONASS antenna offsets in two frames, i.e., IGb14 and IGS R3, considering robot calibrations of the ground receiver antenna models for BDS released by Geo++. We observe that the average offset of Z-PCOs achieves +98.8 mm between BDS official released and the estimated PCOs in IGb14 frame for BDS-3 MEO satellites, whereas the average offset for Z-PCO is about +174.1 mm (about −1.27 ppb at the height of BDS MEO satellites) between the solutions in IGSR3 and IGb14 frame. The phase center solutions are evaluated with orbit boundary disclosures (OBD) as well as the global station coordinates. The orbit consistency benefits from the PCO/PCV estimates, particularly for BDS-2 MEO satellites, of which the 3D RMS (root mean square) OBD is reduced by 50%, whereas 3D OBD achieves about 90.0 mm for BDS-3 MEO satellites. Moreover, the scale bias between BDS-derived station coordinates and IGS legacy solutions in IGb14 frame is reduced from +0.446 ± 0.153 ppb to +0.012 ± 0.112 ppb using PCO/PCV estimates in IGb14, instead of the BDS official released values. Additionally, the residuals of the BDS-derived station heights (after the Helmert transformation) are slightly reduced from 9.65 to 8.62 mm. On the other hand, about +0.226 ± 0.175 ppb is observed between BDS-only coordinate solutions derived from PCO/PCV estimates in IGSR3 frame and the IGS repro3 initial combination. These results demonstrate that the scale inconsistency derived from BDS and Galileo released PCOs is about +1.854 ± 0.191 ppb, and a good consistency of PCO/PCC estimates for BDS in IGb14 and IGSR3 frame with other systems of GPS/ GLONASS antenna offsets is achieved.

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Investigation of Pre-Earthquake Ionospheric and Atmospheric Disturbances for Three Large Earthquakes in Mexico

Geosciences ◽

10.3390/geosciences11010016 ◽

2020 ◽

Vol 11 (1) ◽

pp. 16

Author(s):

Christina Oikonomou ◽

Haris Haralambous ◽

Sergey Pulinets ◽

Aakriti Khadka ◽

Shukra R. Paudel ◽

...

Keyword(s):

Chemical Potential ◽

Atmospheric Model ◽

Satellite System ◽

Seismic Events ◽

Electron Content ◽

Total Electron ◽

Atmospheric Disturbances ◽

Global Ionospheric Maps ◽

Global Navigation Satellite ◽

Large Earthquakes

The purpose of the present study is to investigate simultaneously pre-earthquake ionospheric and atmospheric disturbances by the application of different methodologies, with the ultimate aim to detect their possible link with the impending seismic event. Three large earthquakes in Mexico are selected (8.2 Mw, 7.1 Mw and 6.6 Mw during 8 and 19 September 2017 and 21 January 2016 respectively), while ionospheric variations during the entire year 2017 prior to 37 earthquakes are also examined. In particular, Total Electron Content (TEC) retrieved from Global Navigation Satellite System (GNSS) networks and Atmospheric Chemical Potential (ACP) variations extracted from an atmospheric model are analyzed by performing statistical and spectral analysis on TEC measurements with the aid of Global Ionospheric Maps (GIMs), Ionospheric Precursor Mask (IPM) methodology and time series and regional maps of ACP. It is found that both large and short scale ionospheric anomalies occurring from few hours to a few days prior to the seismic events may be linked to the forthcoming events and most of them are nearly concurrent with atmospheric anomalies happening during the same day. This analysis also highlights that even in low-latitude areas it is possible to discern pre-earthquake ionospheric disturbances possibly linked with the imminent seismic events.

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Estimation of fractional cycle bias for GPS/BDS-2/Galileo based on international GNSS monitoring and assessment system observations using the uncombined PPP model

Satellite Navigation ◽

10.1186/s43020-021-00039-x ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Jin Wang ◽

Qin Zhang ◽

Guanwen Huang

Keyword(s):

Estimation Method ◽

Satellite Orbit ◽

Satellite System ◽

Assessment System ◽

Navigation Satellite ◽

Dual Frequency ◽

Fractional Cycle Bias ◽

The Stability ◽

High Consistency ◽

Global Navigation Satellite

AbstractThe Fractional Cycle Bias (FCB) product is crucial for the Ambiguity Resolution (AR) in Precise Point Positioning (PPP). Different from the traditional method using the ionospheric-free ambiguity which is formed by the Wide Lane (WL) and Narrow Lane (NL) combinations, the uncombined PPP model is flexible and effective to generate the FCB products. This study presents the FCB estimation method based on the multi-Global Navigation Satellite System (GNSS) precise satellite orbit and clock corrections from the international GNSS Monitoring and Assessment System (iGMAS) observations using the uncombined PPP model. The dual-frequency raw ambiguities are combined by the integer coefficients (4,− 3) and (1,− 1) to directly estimate the FCBs. The details of FCB estimation are described with the Global Positioning System (GPS), BeiDou-2 Navigation Satellite System (BDS-2) and Galileo Navigation Satellite System (Galileo). For the estimated FCBs, the Root Mean Squares (RMSs) of the posterior residuals are smaller than 0.1 cycles, which indicates a high consistency for the float ambiguities. The stability of the WL FCBs series is better than 0.02 cycles for the three GNSS systems, while the STandard Deviation (STD) of the NL FCBs for BDS-2 is larger than 0.139 cycles. The combined FCBs have better stability than the raw series. With the multi-GNSS FCB products, the PPP AR for GPS/BDS-2/Galileo is demonstrated using the raw observations. For hourly static positioning results, the performance of the PPP AR with the three-system observations is improved by 42.6%, but only 13.1% for kinematic positioning results. The results indicate that precise and reliable positioning can be achieved with the PPP AR of GPS/BDS-2/Galileo, supported by multi-GNSS satellite orbit, clock, and FCB products based on iGMAS.

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