CODE IGS reference products including Galileo

The International GNSS service (IGS) has been providing precise reference products for the Global Navigation Satellite Systems (GNSS) GPS and (starting later) GLONASS since more than 25 years. These orbit, clock correction, coordinate reference frame, troposphere, ionosphere, and bias products are freely distributed and widely used by scientific, administrative, and commercial users from all over the world. The IGS facilities needed for data collection, product generation, product combination, as well as data and product dissemination, are well established. The Center for Orbit Determination in Europe (CODE) is one of the Analysis Centers (AC) contributing to the IGS from the beginning. It generates IGS products using the Bernese GNSS Software.&#160;In the last decade new GNSS (European Galileo and Chinese BeiDou) and regional complementary systems to GPS (Japanese QZSS and Indian IRNSS/NAVIC) were deployed. The existing GNSS are constantly modernized, offering - among others - more stable satellite clocks and new signals. The exploitation of the new data and their integration into the existing IGS infrastructure was the goal of the Multi-GNSS EXtension (MGEX) when it was initiated in 2012. CODE has been participating in the MGEX with its own orbit and clock solution from the beginning. Since 2014 CODE&#8217;s MGEX (COM) contribution considers five GNSS, namely GPS, GLONASS, Galileo, BeiDou2 (BDS2), and QZSS. We provide an overview of the latest developments of the COM solution with respect to processing strategy, orbit modelling, attitude modelling, antenna calibrations, handling of code and phase biases, and ambiguity resolution. The impact of these changes on the COM products will be discussed.&#160;Recent assessment showed that especially the Galileo analysis within the MGEX has reached a state of maturity, which is almost comparable to GPS and GLONASS. Based on this finding the IGS decided to consider Galileo in its third reprocessing campaign, which will contribute to the next ITRF. Recognizing the demands expressed by the GNSS community, CODE decided in 2019 to go a step further and consider Galileo also in its IGS RAPID and ULTRA-RAPID reference products. We summarize our experiences from the first months of triple-system (ULTRA)-RAPID analysis including GPS, GLONASS, and Galileo. Finally we provide an outlook of CODE&#8217;s IGS analysis with the focus on the new GNSS.

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Assessment of Empirical Troposphere Model GPT3 Based on NGL’s Global Troposphere Products

Sensors ◽

10.3390/s20133631 ◽

2020 ◽

Vol 20 (13) ◽

pp. 3631

Author(s):

Junsheng Ding ◽

Junping Chen

Keyword(s):

Global Navigation Satellite Systems ◽

Tropospheric Delay ◽

Strongly Correlated ◽

International Gnss Service ◽

Total Delay ◽

Average Deviation ◽

Satellite Systems ◽

Global Average ◽

The North ◽

Global Navigation Satellite

Tropospheric delay is one of the major error sources in GNSS (Global Navigation Satellite Systems) positioning. Over the years, many approaches have been devised which aim at accurately modeling tropospheric delays, so-called troposphere models. Using the troposphere data of over 16,000 global stations in the last 10 years, as calculated by the Nevada Geodetic Laboratory (NGL), this paper evaluates the performance of the empirical troposphere model GPT3, which is the latest version of the GPT (Global Pressure and Temperature) series model. Owing to the large station number, long time-span and diverse station distribution, the spatiotemporal properties of the empirical model were analyzed using the average deviation (BIAS) and root mean square (RMS) error as indicators. The experimental results demonstrate that: (1) the troposphere products of NGL have the same accuracy as the IGS (International GNSS Service) products and can be used as a reference for evaluating general troposphere models. (2) The global average BIAS of the ZTD (zenith total delay) estimated by GPT3 is −0.99 cm and the global average RMS is 4.41 cm. The accuracy of the model is strongly correlated with latitude and ellipsoidal height, showing obviously seasonal variations. (3) The global average RMS of the north gradient and east gradient estimated by GPT3 is 0.77 mm and 0.73 mm, respectively, which are strongly correlated with each other, with values increasing from the equator to lower latitudes and decreasing from lower to higher latitudes.

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On the Impact of Channel Cross-Correlations in High-Sensitivity Receivers for Galileo E1 OS and GPS L1C Signals

International Journal of Navigation and Observation ◽

10.1155/2012/132078 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Davide Margaria ◽

Beatrice Motella ◽

Fabio Dovis

Keyword(s):

Cross Correlation ◽

High Sensitivity ◽

Global Navigation Satellite Systems ◽

Integration Time ◽

Noise Component ◽

Satellite Systems ◽

Coherent Integration ◽

Global Navigation Satellite ◽

Correlation Properties ◽

The Impact

One of the most promising features of the modernized global navigation satellite systems signals is the presence of pilot channels that, being data-transition free, allow for increasing the coherent integration time of the receivers. Generally speaking, the increased integration time allows to better average the thermal noise component, thus improving the postcorrelation SNR of the receiver in the acquisition phase. On the other hand, for a standalone receiver which is not aided or assisted, the acquisition architecture requires that only the pilot channel is processed, at least during the first steps of the procedure. The aim of this paper is to present a detailed investigation on the impact of the code cross-correlation properties in the reception of Galileo E1 Open Service and GPS L1C civil signals. Analytical and simulation results demonstrate that the S-curve of the code synchronization loop can be affected by a bias around the lock point. This effect depends on the code cross-correlation properties and on the receiver setup. Furthermore, in these cases, the sensitivity of the receiver to other error sources might increase, and the paper shows how in presence of an interfering signal the pseudorange bias can be magnified and lead to relevant performance degradation.

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The International GNSS Service in a changing landscape of Global Navigation Satellite Systems

Journal of Geodesy ◽

10.1007/s00190-008-0300-3 ◽

2009 ◽

Vol 83 (3-4) ◽

pp. 191-198 ◽

Cited By ~ 944

Author(s):

John M. Dow ◽

R. E. Neilan ◽

C. Rizos

Keyword(s):

Global Navigation Satellite Systems ◽

Navigation Satellite ◽

International Gnss Service ◽

Satellite Systems ◽

Global Navigation ◽

Global Navigation Satellite

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Space weather: risk factors for Global Navigation Satellite Systems

Solar-Terrestrial Physics ◽

10.12737/stp-72202104 ◽

2021 ◽

Vol 7 (2) ◽

pp. 28-47

Author(s):

Vladislav Demyanov ◽

Yury Yasyukevich

Keyword(s):

Space Weather ◽

Solar Radio ◽

Global Navigation Satellite Systems ◽

Navigation Satellite ◽

Satellite Systems ◽

Radio Navigation ◽

Weather Events ◽

Global Navigation Satellite ◽

The Impact ◽

Extreme Space Weather Events

Extreme space weather events affect the stability and quality of the global navigation satellite systems (GNSS) of the second generation (GPS, GLONASS, Galileo, BeiDou/Compass) and GNSS augmentation. We review the theory about mechanisms behind the impact of geomagnetic storms, ionospheric irregularities, and powerful solar radio bursts on the GNSS user segment. We also summarize experimental observations of the space weather effects on GNSS performance in 2000–2020 to confirm the theory. We analyze the probability of failures in measurements of radio navigation parameters, decrease in positioning accuracy of GNSS users in dual-frequency mode and differential navigation mode (RTK), and in precise point positioning (PPP). Additionally, the review includes data on the occurrence of dangerous and extreme space weather phenomena and the possibility for predicting their im- pact on the GNSS user segment. The main conclusions of the review are as follows: 1) the positioning error in GNSS users may increase up to 10 times in various modes during extreme space weather events, as compared to the background level; 2) GNSS space and ground segments have been significantly modernized over the past decade, thus allowing a substantial in- crease in noise resistance of GNSS under powerful solar radio burst impacts; 3) there is a great possibility for increasing the tracking stability and accuracy of radio navigation parameters by introducing algorithms for adaptive lock loop tuning, taking into account the influence of space weather events; 4) at present, the urgent scientific and technical problem of modernizing GNSS by improving the scientific methodology, hardware and software for monitoring the system integrity and monitoring the availability of required navigation parameters, taking into account the impact of extreme space weather events, is still unresolved.

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Towards FAIR GNSS data: challenges and open problems

10.5194/egusphere-egu2020-18398 ◽

2020 ◽

Author(s):

Anna Miglio ◽

Carine Bruyninx ◽

Andras Fabian ◽

Juliette Legrand ◽

Eric Pottiaux ◽

...

Keyword(s):

Research Policy ◽

Global Navigation Satellite Systems ◽

International Gnss Service ◽

Open Problems ◽

Data Repositories ◽

Satellite Systems ◽

Data Practices ◽

Metadata Standards ◽

Global Navigation Satellite ◽

Gnss Data

Nowadays, we measure positions on Earth&#8217;s surface thanks to Global Navigation Satellite Systems (GNSS) e.g. GPS, GLONASS, and Galileo. Activities such as navigation, mapping, and surveying rely on permanent GNSS tracking stations located all over the world. The Royal Observatory of Belgium (ROB) maintains and operates a repository containing data from hundreds of GNSS stations belonging to the European GNSS networks (e.g. EUREF, Bruyninx et al., 2019).&#160;ROB&#8217;s repository contains GNSS data that are openly available and rigorously curated. The curation data include detailed GNSS station descriptions (e.g. location, pictures, and data author) as well as quality indicators of the GNSS observations.However, funders and research policy makers are progressively asking for data to be made Findable, Accessible, Interoperable, and Reusable (FAIR) and therefore to increase data transparency, discoverability, interoperability, and accessibility.In particular, within the GNSS community, there is no shared agreement yet on the need for making data FAIR. Therefore, turning GNSS data FAIR presents many challenges and, although FAIR data has been included in EUREF&#8217;s strategic plan, no practical roadmap has been implemented so far. We will illustrate the specific difficulties and the need for an open discussion including also other communities working on FAIR data.For example, making GNSS data easily findable and accessible would require to attribute persistent identifiers to the data. It is worth noting that the International GNSS Service (IGS) is only now beginning to consider the attribution of DOIs (Digital Object Identifiers) to GNSS data, mainly to allow data citation and acknowledgement of data providers. Some individual GNSS data repositories are using DOIs (such as UNAVCO, USA).&#160; Are DOIs the only available option or are there more suitable types of URIs (Uniform Resource Identifiers) to consider?The GNSS community would greatly benefit from FAIR data practices, as at present, (almost) no licenses have been attributed to GNSS data, data duplication is still an issue, historical provenance information is not available because of data manipulations in data centres, citation of the data providers is far from the rule, etc.To move further along the path towards FAIR GNSS data, one would need to implement standardised metadata models to ensure data interoperability, but, as several metadata standards are already in use in various scientific disciplines, which one to choose?Then, to facilitate the reuse (and long-term preservation) of GNSS data, all metadata should be properly linked to the corresponding data and additional metadata, such as provenance and license information. The latter is a good example up for discussion: despite the fact that &#8216;CC BY&#8217; license is already assigned to some of the GNSS data, other licenses might need to be enabled.&#160;Bruyninx C., Legrand J., Fabian A., Pottiaux E. (2019) &#8220;GNSS Metadata and Data Validation in the EUREF Permanent Network&#8221;. GPS Sol., 23(4), https://doi: 10.1007/s10291-019-0880-9&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

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Save Our Roads from GNSS Jamming: A Crowdsource Framework for Threat Evaluation

Sensors ◽

10.3390/s21144840 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4840

Author(s):

Roi Yozevitch ◽

Revital Marbel ◽

Nir Flysher ◽

Boaz Ben-Moshe

Keyword(s):

Field Experiments ◽

Region Of Interest ◽

Detection Algorithm ◽

Global Navigation Satellite Systems ◽

Dynamic Phenomenon ◽

Satellite Systems ◽

The World ◽

Jamming Detection ◽

Global Navigation Satellite ◽

Coverage Map

Global Navigation Satellite Systems (GNSS) jamming is an acute problem in the world of modern navigation. As more and more applications rely on GNSS for both position and timing, jamming ramifications are becoming more severe. In this paper we suggest a novel framework to cope with these threats. First, a Bayesian jamming detection algorithm is introduced. The algorithm can both detect and track several jammers in a pre-defined region of interest. Then, a jamming coverage map algorithm is offered. Similar to cellular 3G/4G coverage maps, such a map can detect “weak” GNSS reception spots and handle them. Since jamming interference can be a dynamic phenomenon (e.g., a vehicle equipped with a jammer), the coverage map changes with time. Thus, interference patterns can be detected more easily. Utilizing the offered algorithm, both on simulation and field experiments, we have succeeded to localize an arbitrary jammer(s) within the region of interest. Thus, the results validate the viability of the proposed method.

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The Potential Impact of GNSS/INS Integration on Maritime Navigation

Journal of Navigation ◽

10.1017/s0373463307004614 ◽

2008 ◽

Vol 61 (2) ◽

pp. 221-237 ◽

Cited By ~ 12

Author(s):

Terry Moore ◽

Chris Hill ◽

Andy Norris ◽

Chris Hide ◽

David Park ◽

...

Keyword(s):

Field Trials ◽

Global Navigation Satellite Systems ◽

Navigation Systems ◽

Inertial Navigation Systems ◽

Satellite Systems ◽

Time Period ◽

Maritime Navigation ◽

The Uk ◽

Global Navigation Satellite ◽

The Impact

A version of this paper was presented at ENC-GNSS 2007, Geneva. Its reproduction was kindly authorised by the ENC-GNSS 07 Paper Selection Committee.The General Lighthouse Authorities of the UK & Ireland commissioned an assessment of the impact that the integration of Global Navigation Satellite Systems (GNSS) with Inertial Navigation Systems (INS) would have on the aids to navigation (AtoN) services currently provided, and those to be provided in the future. There is concern about the vulnerability of GNSS, and the provision of complementary and backup systems is seen to be of great importance. The integration of INS could provide an independent and self-contained navigation system, for a limited time period, invulnerable to external intentional or unintentional interference, or the influences of changes in national policies. The study included an analysis of the potential use of GNSS-INS in three of the four phases of a vessel's voyage: coastal, port approach and docking. The project consisted of a technology assessment, looking at the different inertial technologies that might be suitable for each phase. This was followed by a technology proving stage, evaluating suitable equipment using simulation and field trials to prove that the claimed performance could be achieved in practice. The final stage of the project was to assess the effects of the availability of such systems on existing and planned aids to navigation services.

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Performance of GPS Positioning in the Presence of Irregularities in the Auroral and Polar Ionospheres during EISCAT UHF/ESR Measurements

Remote Sensing ◽

10.3390/rs13234798 ◽

2021 ◽

Vol 13 (23) ◽

pp. 4798

Author(s):

Habila Mormi John ◽

Biagio Forte ◽

Ivan Astin ◽

Tom Allbrook ◽

Alex Arnold ◽

...

Keyword(s):

Global Navigation Satellite Systems ◽

Positioning Error ◽

Satellite Systems ◽

Gps Positioning ◽

Transient Nature ◽

Radio Signals ◽

E Region ◽

Global Navigation Satellite ◽

The Impact ◽

Residual Errors

Irregularities in the spatial distribution of ionospheric electron density introduce temporal fluctuations in the intensity and phase of radio signals received from Global Navigation Satellite Systems (GNSS). The impact of phase fluctuations originating from irregularities in the auroral and polar ionospheres on GPS positioning was investigated on three days in March 2018 in the presence of quiet-to-moderately disturbed magnetic conditions by combining measurements from GPS and EISCAT UHF/ESR incoherent scatter radars. Two different positioning solutions were analysed: broadcast kinematic (BK) and precise static (PS). The results show that the propagation through irregularities induced residual errors on the observables leading to an increase in the positioning error, in its variability, and in the occurrence of gaps. An important aspect emerging from this study is that the variability of the 3-D positioning error was reduced, and the presence of gaps disappeared when the positioning solutions were evaluated at a 1 s rate rather than at a 30 s rate. This is due to the transient nature of residual errors that are more significant over 30 s time intervals in the presence of irregularities with scale size between few kilometres in the E region to few tens of kilometres in the F region.

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Assessment of geodetic products from Multi-GNSS analyses at the Onsala site

10.5194/egusphere-egu21-14343 ◽

2021 ◽

Author(s):

Periklis-Konstantinos Diamantidis ◽

Grzegorz Kłopotek ◽

Rüdiger Haas ◽

Jan Johansson

Keyword(s):

Global Navigation Satellite Systems ◽

Observation Data ◽

International Gnss Service ◽

Satellite Systems ◽

Triple Frequency ◽

Software Packages ◽

Combined Solution ◽

Gnss Receivers ◽

Global Navigation Satellite ◽

Gnss Data

The dawn of Beidou and Galileo as operational Global Navigation Satellite Systems (GNSS) alongside Global Positioning System (GPS) and GLONASS as well as new features that are now present in all GNSS, such as a triple-frequency setup, create new possibilities concerning improved estimation and assessment of various geodetic products. In particular, the multi-GNSS analysis gives an access to a better sky coverage allowing for improved estimation of zenith wet delays (ZWD) and tropospheric gradients (GRD), and can be used to determine integer phase ambiguities. The Multi-GNSS Experiment (MGEX), as realised by the International GNSS Service (IGS), provides orbit, clock and observation data for all operational GNSS. To take advantage of the new capabilities that these constellations bring, space-geodetic software packages have been retrofitted with Multi-GNSS-compliant modules. Based on this, two software packages, namely GipsyX and c5++, are utilised by way of the static Precise Point Positioning (PPP) approach using six months of data, and an assessment of the derived geodetic products is carried out for several GNSS receivers located at the Onsala core site. More specifically, we perform both single-constellation and multi-GNSS data analysis using Kalman filter and least-squares methods and assess the quality of the derived station positions, ZWD and GRD. A combined solution using all GNSS constellations is carried out and the improvement with respect to station position repeatabilities is assessed for each station. Results from the two software packages are compared with respect to each other and the discrepancies are discussed. Inter-system biases, which homogenise the different time scale that each GNSS operates in, and are necessary for the multi-GNSS combination, are estimated and presented. Finally, the applied inter-system weighting and its impact on the derived geodetic products are discussed.

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Earth Orientation Parameter Estimation by Integrating VLBI and GNSS on the Observation Level

10.5194/egusphere-egu21-616 ◽

2021 ◽

Author(s):

Jungang Wang ◽

Kyriakos Balidakis ◽

Maorong Ge ◽

Robert Heinkelmann ◽

Harald Schuh

Keyword(s):

Polar Motion ◽

Reference Frames ◽

Global Navigation Satellite Systems ◽

Satellite Systems ◽

Earth Orientation ◽

Long Baseline ◽

Space Geodetic Techniques ◽

Global Navigation Satellite ◽

The Impact ◽

Globally Distributed

The terrestrial and celestial reference frames are linked by the Earth Orientation Parameters (EOP), which describe the irregularities of the Earth's rotation and are determined by the space geodetic techniques, namely, Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). The satellite geodetic techniques (SLR, GNSS, and DORIS) cannot determine the UT1-UTC or celestial pole offsets (CPO), rendering VLBI the only technique capable of determining full EOP set. On the other hand, the GNSS technique provides precise polar motion estimates due to the continuous observations from a globally distributed network. Integrating VLBI and GNSS provides the full set of EOP and guarantees a superior accuracy than any single-technique solution.In this study we focus on the integrated estimation of the full EOP set from GNSS and VLBI. Using five VLBI continuous observing campaigns (CONT05&#8211;CONT17), the GNSS and VLBI observations are processed concurrently in a common least-squares estimator. The impact of applying global ties (EOP), local ties, and tropospheric ties, and combinations thereof is investigated. The polar motion estimates in integrated solution are dominated by the huge GNSS observations, and the accuracy in terms of weighted root mean squares (WRMS) is ~40&#160;&#956;as compared to the IERS 14 C04 product, which is much better than that of the VLBI-only solution. The UT1-UTC and CPO in the integrated solution also show slight improvement compared to the VLBI-only solution. Moreover, the CPO agreement between the two networks in CONT17, i.e., the VLBA and IVS networks, shows an improvement of 20% to 40% in the integrated solution with different types of ties applied.

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