G1.2

G1 EDI

In recent years we have witnessed a remarkable progress in terms of signals, services and satellite deployment of Global Navigation Satellite Systems (GNSS). The modernisation of fully operational GNSS systems and the development of new constellations, have seen us move towards a new stage of multi-constellation and multi-frequency observations. Meanwhile, the huge technology development provided high-grade GNSS equipment able to collect measurements at much higher rates, up to 100 Hz, hence opening new possibilities. Moreover, the recent progress in low-cost GNSS chipsets is catalyzing an expansion of traditional satellite navigation to novel areas of science and industry.
Therefore, on one side, the new developments in GNSS stimulate a broad range of new applications for solid and fluid Earth investigations, both in post-processing and in real-time; on the other side, this results in new problems and challenges in data processing which boost GNSS research. Algorithmic advancements are needed to address the opportunities and challenges in enhancing the accuracy, availability, interoperability and integrity of high-precision GNSS applications.
This session is a forum to discuss new developments in high-precision GNSS algorithms and applications in Geosciences; in this respect, contributions from other branches in Geosciences (geodynamics, seismology, tsunamis, ionosphere, troposphere, etc.) are very welcome.
We encourage, but not limit, submissions related to:
- Processing algorithms in high-precision GNSS,
- Multi-GNSS benefit for Geosciences,
- Multi-GNSS processing and product standards,
- Inter-system and inter-frequency biases,
- GNSS products for high-precision applications (orbits, clocks, UPDs, etc.),
- Precise Point Positioning (PPP, PPP-RTK) and Real Time Kinematic (RTK),
- High-rate GNSS,
- Low-cost receiver and smartphone GNSS observations for precise positioning, navigation and geoscience applications,
- GNSS and other sensors (accelerometers, INS, etc.) integration for high-rate applications,
- Troposphere and ionosphere modelling in GNSS positioning and applications,
- CORS services for Geosciences (GBAS, Network-RTK, etc.),
- Precise Positioning of EOS platforms,
- Precise Positioning for natural hazards prevention,
- Monitoring crustal deformation and the seismic cycle of active faults,
- GNSS and early-warning systems,
- GNSS reflectometry.

Convener: Jacek Paziewski | Co-conveners: Elisa Benedetti, Felix Perosanz, Mattia Crespi, Jianghui Geng
Presentations
| Tue, 24 May, 08:30–11:15 (CEST)
 
Room -2.91

Session assets

Session materials

Presentations: Tue, 24 May | Room -2.91

Chairpersons: Pawel Wielgosz, Mattia Crespi, Jianghui Geng
08:30–08:40
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EGU22-12264
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solicited
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Highlight
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On-site presentation
Norman Teferle, Addisu Hunegnaw, Hüseyin Duman, Hakki Baltaci, Yohannes Getachew Ejigu, and Jan Dousa

Climate change has led to an increase in the frequency and severity of weather events with intense precipitation and subsequently a greater susceptibility to flash flooding of cities worldwide. As a result, accurate fore- and now-casting of imminent extreme precipitation has become critical for the warning and mitigation of these hydro-meteorological hazards. Networks of ground-based Global Navigation Satellite System (GNSS) stations enable the measurement of integrated water vapour along slant pathways, providing three-dimensional (3D) water vapour distributions at low cost and in real-time. This makes these data a valuable complementary source of information for tracking storm events and predicting their paths. However, it is well established that multipath effects at GNSS stations do impact incoming signals, especially at low elevations. While the GNSS products for meteorology to date consist predominantly of estimates of zenith total delay and horizontal gradients, these products are not optimal for constraining the 3D distribution of water vapour above a station. The direct use of slant delays counteracts this lack of azimuthal information but is more susceptible to multipath errors at low elevations. This study investigates the impact of multipath-corrected slant wet delay (SWD) estimates on tracking extreme weather events using the convective storm event over Bulgaria, Greece and Turkey on July 27, 2017, which resulted in flash floods and significant property damage. First, we recovered the one-way SWD by adding GNSS post-fit phase residuals, representing the non-isotropic component of the SWD, i.e., the higher-order inhomogeneity. As the MP errors in the GNSS phase observables can significantly affect the SWD from individual satellites, we employed an averaging strategy for stacking the post-fit phase residuals obtained from our Precise Point Positioning (PPP) processing strategy to generate station-specific MP correction maps. The spatial stacking was carried out in congruent cells with an optimal resolution in elevation and azimuth at the local horizon but with decreasing azimuth resolution as the elevation angle increases. This permits an approximately equal number of observations allocated to each cell. Using these MP correction maps in a final step, the one-way SWD were improved to employ them for the analysis of the weather event. We found that the non-isotropic component of the one-way SWD contributes up to 11% of the SWD estimates. Moreover, we validated the SWD between ground-based water-vapour radiometry and GNSS-derived SWD for different elevation angles. Furthermore, the spatio-temporal fluctuations in the SWD as measured by GNSS closely mirrored the moisture field from the ERA5 re-analysis associated with this weather event. By employing an adequate windowing system for generating these MP correction maps in combination with high-precision real-time GNSS analysis, it is possible to provide improved SWD estimates for the tracking of severe weather events.

How to cite: Teferle, N., Hunegnaw, A., Duman, H., Baltaci, H., Ejigu, Y. G., and Dousa, J.: On the Impact of GNSS Multipath Correction Maps on Slant Wet Delays for Tracking Severe Weather Events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12264, https://doi.org/10.5194/egusphere-egu22-12264, 2022.

08:40–08:45
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EGU22-4504
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Virtual presentation
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Peter Steigenberger, André Hauschild, and OIiver Montenbruck
More than ten years after the launch of the first satellite of the Japanese Quasi-Zenith Satellite System (QZSS), a replenishment satellite for this spacecraft was launched into inclined geo-synchronous orbit (IGSO) in October 2021. Triple-frequency signal transmission of QZS-1R started on November 14, 2021. In the same month, Cabinet Office, Government of Japan published satellite metadata of QZS-1R including mass, center of mass coordinates, laser retro-reflector offsets, satellite antenna phase center offsets and variations, transmit power, attitude law, as well as spacecraft dimensions and optical properties.
Precise orbit and clock parameters of QZS-1R are estimated with the NAPEOS software. The performance of a box-wing model derived from the satellite metadata is evaluated by day boundary discontinuities, orbit overlaps as well as Satellite Laser Ranging residuals. The analysis of the QZS-1R clock parameters estimated together with the orbits is complemented by a one-way carrier phase clock analysis of selected GNSS receivers connected to highly stable clocks in order to study also the short-term clock behavior.
Like previous QZSS IGSO satellites, QZS-1R transmits the L1 Sub-meter Level Augmentation Service (SLAS) via a dedicated antenna separated about 1.2 m from the main navigation antenna. Therefore, simultaneous observations of, e.g., the L1C/A and the L1 SLAS signals allow to determine the QZS-1R attitude. Attitude estimates from a regional network of eight stations are presented and compared to the nominal attitude of the spacecraft.

How to cite: Steigenberger, P., Hauschild, A., and Montenbruck, O.: Orbit, clock and attitude analysis of QZS-1R, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4504, https://doi.org/10.5194/egusphere-egu22-4504, 2022.

08:45–08:50
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EGU22-11628
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ECS
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On-site presentation
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Emilio José Calero Rodríguez, Arturo Villiger, Stefan Schaer, Rolf Dach, and Adrian Jäggi

The use of zero-difference processing schemes becomes more and more popular within the GNSS (Global Navigation Satellite Systems) community. This change from double- to zero-difference approaches increases the demand of PPP-AR (Ambiguity Resolution for Precise Point Positioning) enabling products. Those products can be created in two ways, either estimate the geometrical part (orbits) based on a double-difference global network solution with a separate zero-difference solution for the clocks and phase biases, or in a combined zero-difference solution. The latter one allows a more flexible approach; however, the challenge lies in the handling of the increased number of parameters and ambiguity resolution.

The estimation of combined orbit and clock zero-difference enabling products needs a thought-out design of the processing strategy, where the elimination and back-substitution steps are vital to deal with the large number of parameters. Nonetheless, the amount of ambiguity parameters dramatically grows with an increasing size of the network, posing some computational limitations, since they should not be eliminated for a successful ambiguity resolution. Such a restriction originates from fixing float orbits: their accuracy does not allow to estimate reliable ambiguity parameters. To cope with that, we propose a new algorithm capable to decouple them from the orbits, allowing to fix between-satellite ambiguities in a later station-wise parallelisation.

On the poster, we describe selected details on the ambiguity resolution strategy that we have developed. The obtained results are characterized and compared to other solutions using classical ambiguity resolution schemes.

How to cite: Calero Rodríguez, E. J., Villiger, A., Schaer, S., Dach, R., and Jäggi, A.: Combined orbit and clock zero-difference solution at CODE: ambiguity resolution strategy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11628, https://doi.org/10.5194/egusphere-egu22-11628, 2022.

08:50–08:55
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EGU22-2477
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On-site presentation
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Krzysztof Sośnica, Radosław Zajdel, Grzegorz Bury, Kamil Kazmierski, Tomasz Hadaś, Marcin Mikoś, Maciej Lackowski, and Dariusz Strugarek

Although the full operational capability of the Galileo system has not been officially announced as yet, the European GNSS, Galileo, has already remarkably contributed to geodesy, positioning, navigation, timing, and fundamental physics. Galileo metadata with the details on the satellite construction and surface properties allow for the development of the high-accuracy satellite macro-models and precise orbit determination. Two integrated onboard observation techniques – satellite laser ranging (SLR) and microwave GNSS – allow for the integration of space geodetic techniques and co-location in space. Calibrated satellite and receiver antenna offsets allow for scale realization and scale transfer for the reference frames.

GNSS orbits of superior quality constitute the basis for other geodetic products, such as Earth rotation parameters, station coordinates, geocenter motion, international terrestrial reference frames, tropospheric and ionospheric delays. Moreover, the high-quality orbits and clocks installed on a pair of Galileo satellites launched onto eccentric orbits allow for studying effects emerging from general relativity, both related to the time redshift, as well as to orbital Schwarzschild, Lense-Thirring, and de Sitter effects constituting the essential issues of fundamental physics. Finally, high-quality and frequently-updated broadcast orbits together with very stable clocks onboard Galileo assure the superior accuracy of the real-time positioning when compared to other GNSS.

We discuss the advantages and limitations of the Galileo system in terms of its applicability to geodesy, concentrating on daily and sub-daily Earth rotation parameters – polar motion and length-of-day variability, station coordinates, and geocenter motion. We address the system-specific errors discovered in GPS, GLONASS, and Galileo time series due to different satellite revolution periods, aliasing effects, tidal constituents, and orbit modeling issues. Some orbit modeling issues related, e.g., to thermal effects, remain unresolved, however, their impact may be mitigated by estimating empirical parameters and the combination of laser and microwave observations. The co-location in space onboard Galileo paves new opportunities for the realization of the reference frames tied in space, onboard GNSS satellites. We provide results on the recent developments of precise orbit determination and co-location in space based on integrated SLR and GNSS observations. Eventually, we discuss the latest applications of high-accurate orbits of Galileo satellites in near-circular and eccentric orbits toward the verification of the effects emerging from general relativity.

How to cite: Sośnica, K., Zajdel, R., Bury, G., Kazmierski, K., Hadaś, T., Mikoś, M., Lackowski, M., and Strugarek, D.: Contribution of the Galileo system to space geodesy and fundamental physics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2477, https://doi.org/10.5194/egusphere-egu22-2477, 2022.

08:55–09:00
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EGU22-12557
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ECS
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On-site presentation
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Sebastian Strasser, Torsten Mayer-Gürr, Barbara Süsser-Rechberger, and Patrick Dumitraschkewitz

Signal biases are hardware delays that occur during the transmission and reception of GNSS signals. On the satellite side, there is a delay between the generation of a signal and its transmission at the antenna. The same is the case on the receiver side, where a delay occurs between signal reception at the antenna and the actual measurement of a specific signal in the receiver. As the name suggests, code biases refer to the delays affecting code observations. Similarly, phase observations are affected by phase biases. In general, signal biases differ per constellation, satellite, frequency, signal attribute, as well as receiver hardware and settings.

The main issue with signal biases is that they are usually not known. Therefore, they have to be estimated during GNSS processing. However, the relative nature of GNSS observations prevents the estimation of absolute signal biases. This results in several rank deficiencies in the normal equation system when signal biases are estimated together with other geodetic parameters in a global multi-GNSS processing.

We present a general approach based on eigenvalue analysis to solve these rank deficiencies. Therefore, the co-estimation of pseudo-absolute transmitter and receiver signal biases in our multi-GNSS processing becomes possible. This approach also enables ambiguity resolution of GLONASS phase obervations.

How to cite: Strasser, S., Mayer-Gürr, T., Süsser-Rechberger, B., and Dumitraschkewitz, P.: Estimable phase and code biases in the frame of global multi-GNSS processing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12557, https://doi.org/10.5194/egusphere-egu22-12557, 2022.

09:00–09:05
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EGU22-2566
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ECS
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On-site presentation
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Patrick Dumitraschkewitz, Torsten Mayer-Gürr, and Sebastian Strasser

Global navigation satellite systems (GNSS) are integral to a wide array of scientific and commercial applications. Precise orbit determination of satellites in low Earth orbit relies on high-quality GNSS products. Examples of such satellites are those of the Copernicus Earth observation program of the European Union or the satellite gravimetry missions GRACE/GRACE-FO and GOCE. Numerous ground-based applications also require these products, for example: estimation of terrestrial water storage variations, earthquake monitoring, GNSS reflectometry, tropospheric and ionospheric research, surveying, or civil engineering. Furthermore, GNSS-derived station coordinates play an important role in the determination of the International Terrestrial Reference Frame. The analysis centres of the International GNSS Service (IGS) generate such products by processing observations from a global network of ground stations to one or more GNSS constellations.

So far, this kind of processing only incorporates elevation-dependent a priori modelling of observation variances and disregards temporal correlations. Meanwhile, numerous studies have shown the positive impact the incorporation of sophisticated stochastic modelling has on GNSS processing and resulting products. However, there have not been any large-scale investigations regarding the impact of stochastic modelling of observation noise on global GNSS processing.

In this contribution, we discuss a post-fit residuals approach for deriving temporal correlations in global multi-GNSS processing and their limitations. We used several years of observations and a selected IGS network of ground stations. Based on this data we analysed the post-fit residuals and the derived temporal correlations per station with respect to their seasonal effects, specific used receivers, antennas, and different transmitter signal types.

How to cite: Dumitraschkewitz, P., Mayer-Gürr, T., and Strasser, S.: Empirical stochastic modeling of observation noise in global GNSS network processing, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2566, https://doi.org/10.5194/egusphere-egu22-2566, 2022.

09:05–09:10
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EGU22-1146
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ECS
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On-site presentation
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Johannes Kröger, Tobias Kersten, Yannick Breva, Mareike Brekenkamp, and Steffen Schön

For highly precise and accurate positioning and navigation solutions with GNSS, it is mandatory to take all error sources – including phase center corrections (PCC) – adequately into account. These corrections are provided by different calibration facilities and are published in the official IGS antenna exchange format (ANTEX) file for several geodetic antennas.

Currently, the IGS antenna working group (AWG) is discussing which metrics should be used as a basis for accepting new calibration facilities as an official IGS calibration facility. To this end, requirements have to be set for comparing different sets of PCC for the same type of antenna.

Mostly, characteristic values of difference patterns (dPCC) are analysed, e.g. maximum deviations, RMS of dPCC, or percentage of dPCC values that are smaller than 1 mm. For users and station providers, however, it is most interesting to investigate the impact of dPCC on geodetic parameters, e.g. topocentric coordinate deviations and troposphere estimates. Since the impact is not only depending on the antenna in use and the station’s location but also on the applied processing strategies, a standardized comparison strategy is needed.

In this contribution, we present the impact of different PCC values on geodetic parameters using a standardized simulation approach. We show results for several globally distributed stations using different processing strategies and their respective impact on the geodetic parameters. This includes the application of different elevation cut-off angles, observation weightings w.r.t satellite coverages and elevation angles as well as use of different frequencies and linear combinations. The obtained results are analysed in detail, repeated behaviours are grouped and compared to widely used characteristic values of dPCC. Thus, an overall conclusion of the similarity of different PCC models can not only be drawn on the pattern level, but also their impact on geodetic parameters can be assessed.

How to cite: Kröger, J., Kersten, T., Breva, Y., Brekenkamp, M., and Schön, S.: Impact of Different Phase Center Correction Values on Geodetic Parameters: A Standardized Simulation Approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1146, https://doi.org/10.5194/egusphere-egu22-1146, 2022.

09:10–09:15
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EGU22-11421
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Presentation form not yet defined
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Lucie Rolland, Edhah Munaibari, Florian Zedek, Sladen Anthony, T. Dylan Mikesell, Coïsson Pierdavide, and Delouis Bertrand

Large earthquakes strongly shake the upper atmosphere, leaving distinctive signatures in total electron content (TEC) measured using GNSS trans-ionospheric monitoring. The ionosphere is particularly sensitive to brutal uplift motions of the ground or sea surface, triggering upward propagating mechanical waves. In specific conditions that we will detail in this presentation, GNSS-TEC measurements contain critical information on the immediate consequences of an earthquake. If accurate and provided rapidly, independent knowledge of the sea surface deformation extent and distribution could feed tsunami early warning systems.

Radio waves emitted by GNSS satellites integrate the ionospheric electron density wavefield along their propagation path. At ground level, GNSS receivers can only sense the TEC, which contains the contribution of the ionospheric wavefronts. These wavefronts are destructively or constructively integrated, depending on the involved geometry of observation. In some conditions, even a close station will not sense the TEC perturbation, while a station located 200 km away will sense large TEC fluctuations. This complex behavior mainly depends on the line-of-sight 3D geometry crossing the electron density perturbation. To study how this geometry can affect the estimation of the generating motion, we first build TEC sensitivity maps and highlight more blind or sensitive zones at the Earth’s surface. We apply the procedure to past tsunamigenic earthquakes at mid and low latitudes. Those are the 2010 Mw 7.6 Mentawaii earthquake (Indonesia), the 2016 Mw 7.8 Kaikoura earthquake (New Zealand), and the 2010 Mw 8.8 Maule earthquake (Chile). The TEC sensitivity maps allow us to investigate how the reciprocal locations of the available GNSS stations and satellites can affect the localization of the origin of the ionospheric disturbances. In a second step, we build localization maps with a full waveform method (IonoSeis software) and, where possible, with a time delay fitting method. We compare the resulting maps with the Earth’s surface deformation distribution estimated by more conventional seismo-geodetic methods. We finally show how the extension and densification of GNSS networks with multi-GNSS low-cost receivers and enhanced ionosphere monitoring could help mitigate tsunamis better.

How to cite: Rolland, L., Munaibari, E., Zedek, F., Anthony, S., Mikesell, T. D., Pierdavide, C., and Bertrand, D.: Rapid characterization of tsunami sources with GNSS-TEC ionospheric monitoring , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11421, https://doi.org/10.5194/egusphere-egu22-11421, 2022.

09:15–09:20
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EGU22-7150
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On-site presentation
Jacek Paziewski, Yaqi Jin, Wojciech J. Miloch, Rafal Sieradzki, Wojciech Jarmolowski, Manuel Hernandez-Pajares, Pawel Wielgosz, Jens Berdermann, Mainul Hoque, Per Høeg, Alberto Garcıa-Rigo, Haixia Lyu, Beata Milanowska, Lasse B. N. Clausen, Enric Monte-Moreno, and Raul Orús-Pérez

Ionospheric irregularities impair GNSS signals and, in turn, affect the performance of GNSS positioning. Such effects are especially evident for the high latitudes, which are currently gaining the attention of research and industry branches. These activities should be supported with reliable positioning and navigation services. Such needs motivate us to assess, for the first time, the impact of ionospheric irregularities on GNSS positioning performance in Greenland. We fill the gap and evaluate the performance of positioning methods that were not investigated comprehensively until now but meet the demands of a wide range of users. In this regard, we address the needs of mass-market users that most frequently employ single-frequency receivers and expect a meter to submeter-level accuracy in an absolute mode; and the users who require the highest precision solution based on geodetic-grade dual-frequency receivers. We take advantage of the datasets collected at the GNET permanent network in Greenland during three ionospheric storms, namely the St. Patrick storm of March 17, 2015, June 22, 2015, and August 25–­26, 2018. We discover a significant impact of the ionospheric disturbances on the ambiguity resolution performance and the accuracy of the float solution in RTK positioning. Next, assessing the single-frequency ionospheric-free PPP, we demonstrate that the model is generally unaffected by the ionospheric disturbances. Hence, the model is predestined for the application by the users of single-frequency receivers in the areas of frequent ionospheric disturbances. Finally, based on the observation analyses, we revealed that phase signals on the L2 frequency band are more prone to the cycle slips induced by ionospheric irregularities than those transmitted on the first one.

How to cite: Paziewski, J., Jin, Y., Miloch, W. J., Sieradzki, R., Jarmolowski, W., Hernandez-Pajares, M., Wielgosz, P., Berdermann, J., Hoque, M., Høeg, P., Garcıa-Rigo, A., Lyu, H., Milanowska, B., Clausen, L. B. N., Monte-Moreno, E., and Orús-Pérez, R.: On the implications of ionospheric disturbances for GNSS precise positioning: a case study of Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7150, https://doi.org/10.5194/egusphere-egu22-7150, 2022.

09:20–09:25
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EGU22-5780
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ECS
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On-site presentation
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Grzegorz Kłopotek, Benedikt Soja, Mudathir Awadaljeed, Laura Crocetti, Markus Rothacher, Linda See, Rudi Weinacker, Tobias Sturn, Ian McCallum, and Vicente Navarro

    Global Navigation Satellite System (GNSS) is a well-recognized observation technique in studies on the ionosphere due to its sensitivity to the total electron content (TEC). The era of modern smartphones, running on Android version 7.0 and higher, facilitates the acquisition of raw dual-frequency GNSS measurements, paving the way for the GNSS community data to be potentially exploited in geoscience applications. One can assume that the continuous progress in this domain may result in future in a performance of those smart devices reaching the level of GNSS receivers (and antennas) used for atmospheric monitoring. The prospective utilization of a very large number of GNSS-capable smartphones, as a dynamic crowdsourcing receiver network, could form thus an attractive source of complementary GNSS data, allowing to significantly increase the spatial resolution of observations available for the analysis and cover areas of the globe where GNSS receivers are not yet present. The enormous volume of prospective GNSS community data brings, however, major challenges related to data acquisition, its storage, and subsequent processing for deriving various parameters of interest, also in near-real time. The same applies to the analysis of such huge and heterogeneous data sets, requiring a dedicated approach in order to exploit the data in a thorough manner and fully benefit from such a concept.
Application of Machine Learning Technology for GNSS IoT data fusion (CAMALIOT) is an ongoing ESA NAVISP project with activities covering acquisition of GNSS observations from modern smartphones and development of the dedicated infrastructure regarding GNSS processing and machine learning at scale. An Android application, developed within that project, is utilized to retrieve code and phase observations from the modern generation of smartphones. The acquired user-specific data is available to the user in the form of RINEX3-compliant files and can be uploaded by the user to the central server for subsequent processing.
This contribution highlights the CAMALIOT project in relation to the ionosphere and provides information on the developed Android application, data ingestion and processing, complemented with methodology and initial results related to the TEC retrieval based on smartphone data collected in the vicinity of geodetic GNSS receivers, with the latter used for deriving reference time series. Concerning the smartphone data, the amount and quality of observations are much lower compared to the high-grade GNSS equipment and a dedicated pre-processing stage is needed in order to discard bad observations in a proper manner. An apparent correlation between the data quality, utilized frequency bands and satellite constellation involved is visible too. This area of GNSS still suffers from the limitations related mainly to the components comprising the smartphone, resulting in the lower quality of the acquired GNSS observations, compared to those obtained with the use of high-grade GNSS receivers and antennas. This translates to a greater susceptibility to multipath as well as a much more frequent occurrence of observation gaps and cycle slips, affecting the data availability and continuity of the carrier-phase measurements.

How to cite: Kłopotek, G., Soja, B., Awadaljeed, M., Crocetti, L., Rothacher, M., See, L., Weinacker, R., Sturn, T., McCallum, I., and Navarro, V.: Total Electron Content Monitoring Complemented with Crowdsourced GNSS Observations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5780, https://doi.org/10.5194/egusphere-egu22-5780, 2022.

09:25–09:30
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EGU22-3870
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Virtual presentation
Rafal Sieradzki

The polar ionosphere is characterized by massive structures, known as patches, resulting from intake of mid-latitude plasma or, to a lesser extent, from particle precipitation. The occurrence of patches is an object of multi-instrumental investigations performed with various space- and ground-based techniques, involving among others the measurements of Global Navigation Satellite Systems. With regard to the latter approach, the patch definition has to be reformulated to the electron density accumulated along a signal path. This step requires an additional validation of the relation between an elevation angle of GNSS measurements and an integrated enhancement of plasma.

The work compares polar patch signatures observed in GNSS time series during a maximum solar activity. The assessment of integrated patch enhancement was realized with relative STEC values that are computed for several GNSS stations located in the northern polar cap. Investigating the results at different elevation angles, one can observe a lack of typical geometrical dependency of relative STEC. We believe this effect is related to an approximately spherical shape of patches. Such a conclusion seems to be confirmed by a similar enhancement observed for measurements with different orientations. According to the obtained results, we find this is justified to use STEC as an indicator of patch enhancement for GNSS data.    

How to cite: Sieradzki, R.: A study on the relation between an elevation angle of GNSS measurements and an integrated plasma enhancement of polar patches., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3870, https://doi.org/10.5194/egusphere-egu22-3870, 2022.

09:30–09:35
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EGU22-5477
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ECS
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On-site presentation
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Beata Milanowska, Paweł Wielgosz, Mainul Hoque, Dariusz Tomaszewski, Wojciech Jarmołowski, Anna Krypiak-Gregorczyk, Karolina Krzykowska-Piotrowska, and Jacek Rapiński

The adverse effects of ionospheric delays limit the positioning accuracy of single-frequency GNSS users. To mitigate these effects, GNSS system providers make several ionospheric delays models available for their global users. For example, the GPS has offered the Klobuchar model from the beginning. More recently, Galileo users can use the NeQuick G model. In the meantime, several independent models available for real-time navigation have emerged. Recent examples are the NTCM (Neustrelitz Total Electron Content Model) correction model provided by the German Aerospace Center (DLR) and real-time global ionosphere maps (RT-GIMs) provided by the National Centre for Space Studies (CNES).

In this contribution, we evaluate the performance of several global ionospheric delay correction models in SPP mode. We used single-frequency pseudorange data from 12 GNSS stations distributed globally, covering different latitudes for the evaluation. The test data includes GNSS observations from DOY 93/2020 to DOY 80/2021, covering almost one full year of increasing solar activity. We validated the performance of the NTCM-G model driven by the Galileo Az parameters against the Klobuchar, NeQuick 2, NeQuick G, and CNES RT GIMs models. Finally, we compared the results to reference solutions obtained with CODE GIM and also using the ionosphere-free linear combination. We showed that NTCM-G corrections presented accuracy comparable with the NeQuick G model and better than the Klobuchar one.

How to cite: Milanowska, B., Wielgosz, P., Hoque, M., Tomaszewski, D., Jarmołowski, W., Krypiak-Gregorczyk, A., Krzykowska-Piotrowska, K., and Rapiński, J.: Evaluation of NTCM-G ionospheric delay correction model for single-frequency SPP users., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5477, https://doi.org/10.5194/egusphere-egu22-5477, 2022.

09:35–09:40
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EGU22-12698
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ECS
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Virtual presentation
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Peng Feng, Rüdiger Haas, Gunnar Elgered, and Joakim Strandberg

During the last decade, GNSS interferometric reflectometry (GNSS-IR) has shown great potential for sea level monitoring. In combination with geodetic positioning, GNSS-IR provides a possibility to directly link the sea level measurements to the global terrestrial reference frame. However, many error sources can still be better modeled, and the accuracy of GNSS-IR sea level measurements can be improved. Specifically, we revise the tropospheric error model in ground-based GNSS-IR for sea level applications. Unlike GNSS positioning applications, in GNSS-IR the bending effect is as important as the delay effect. Also, usually very low elevation angle observations are used in GNSS-IR, which makes the atmospheric impact even more important. For the bending effect, we propose a new calculation which takes into account the water vapour content and utilizes the widely used mapping function approach to account for the elevation dependence. For the GNSS-IR atmospheric delay, we revise the geometry of the GNSS signal path for the case of coastal GNSS-IR where the antenna is within < 100 m from the sea surface. The atmospheric delay for the reflected signal is separately evaluated at the surface specular reflection point. The delay from the satellite to the reflection point and the direct signal can both be derived from the zenith delay and mapping function, at their respective local coordinates. The delay from the reflection point to the antenna is obtained assuming an average layer refractivity. We validated our model with ray-tracing radiosonde data. At 2° elevation angle, the new method can correct > 98 % of the atmospheric bending effect, compared to about 88 % with the previously adopted approach. With fewer approximations than the previous approach (directly using the mapping function), the new delay error model is also more accurate but with less absolute improvement of about 3 % compared to the previously existing model.

How to cite: Feng, P., Haas, R., Elgered, G., and Strandberg, J.: Calibrating tropospheric errors on ground-based GNSS reflectometry: calculation of bending and delay effects, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12698, https://doi.org/10.5194/egusphere-egu22-12698, 2022.

09:40–09:45
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EGU22-1304
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ECS
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On-site presentation
Faruk Can Durmus, Ali Hasan Dogan, and Bahattin Erdogan

Global Navigation Satellite Systems (GNSS) are used for different geodetic applications such as monitoring deformations and determining plate velocities. Precise positions of stations are needed for such studies. GNSS error sources should be modelled or eliminated to achieve precise coordinates. Some error sources (e.g., receiver and satellite clock errors) can be eliminated by differencing techniques in relative point positioning. However, in precise point positioning (PPP) these errors should be modelled since the technique uses un-differenced and ionosphere-free combinations. Tropospheric signal delay, one of the atmospheric error sources of GNSS, does not depend on the signal frequency; hence, it should be modelled. This delay is modelled in zenith direction, although it occurs along the signal path. This relation is provided with tropospheric mapping functions (MFs). In this study, the effects of MFs for different station heights and latitudes have been investigated. The datasets of 294 continuously operating reference stations were processed with Jet Propulsion Laboratory’s GipsyX v1.2 software. Moreover, the datasets were subdivided into non-overlapping periods between 2 and 24 h to examine the effects of MFs on different session durations.

 

Keywords: GPS, PPP, Troposphere, Mapping Functions, GipsyX v1.2

How to cite: Durmus, F. C., Dogan, A. H., and Erdogan, B.: Investigation of the effect of tropospheric mapping functions for different station heights and latitudes on PPP, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1304, https://doi.org/10.5194/egusphere-egu22-1304, 2022.

09:45–09:50
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EGU22-245
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ECS
|
On-site presentation
Gizem Sezer and Bahattin Erdogan

Global Navigation Satellite Systems (GNSS) can be operated 24 hours in all weather conditions; thus, it is widely preferred in many geodetic studies. With GNSS, position information can be obtained with high accuracy. However, in order to achieve precise position, GNSS error sources such as atmospheric effects should be eliminated. Since ionospheric delay depends on the frequency of the transmitted signal, it can be eliminated with dual-frequency receivers. But, the tropospheric delay does not depend on the signal frequency. Therefore, it can not be eliminated by signal combinations. The effect of tropospheric delay depends on various factors such as station’s altitude, signal direction, cut off angle, atmospheric pressure, temperature and relative humidity. Although tropospheric delays occur along the signal path, these delays are estimated in zenith direction. Tropospheric mapping functions (MFs) are used to project slant to zenith delay. In this study, the effects of most preferred MFs in the literature, which are Global Mapping Function (GMF), Niell Mapping Function (NMF) and Vienna Mapping Function 1 (VMF1), on position accuracy was investigated. For this aim, three networks with different baseline lengths, (1) less than 100 km, (2) between 100 km and 500 km and (3) more than 500 km, were designed including 10 stations. In addition, to examine the seasonal effect of the MFs, four month dataset (January – April – July – October) were selected. These dataset were processed with the Bernese software implementing relative point positioning method by fixing 3 stations. Moreover, the dataset were subdivided into different session durations (2-3-4-6-8-12 and 24 hours) and the effect of session duration on position accuracy was analysed. According to the initial results, it can be concluded that the position accuracy on short session duration depends on the baseline length and more accurate results were obtained in the shortest network. In addition, more accurate results were obtained by VMF1 for the up component; however, for the horizontal components, there were no significant differences between the MFs.

 

Keywords: GPS, Accuracy, Troposphere, Mapping Functions, Bernese

How to cite: Sezer, G. and Erdogan, B.: Effects of different tropospheric mapping functions on GPS positioning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-245, https://doi.org/10.5194/egusphere-egu22-245, 2022.

09:50–09:55
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EGU22-7899
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ECS
|
On-site presentation
|
Katarzyna Stępniak and Jacek Paziewski

The aim of the study is to investigate the quality of the tropospheric estimates obtained with the use of the latest dual-frequency low-cost GNSS receivers. We aim to verify if the low-cost receivers may provide information on the parameters that describe the state of the troposphere with accuracy and reliability close to that of high-grade receivers. In this way, we address a scientific question on the potential usability of such receivers for climate applications. We investigate selected GNSS tropospheric estimates such as zenith tropospheric delays (ZTDs) and horizontal gradients. ZTD accuracy is validated in comparison to ERA5, which is the fifth generation reanalysis for the global climate and weather produced by European Centre for Medium-Range Weather Forecasts (ECMWF).

The experiment is based on GNSS data collected during two measurement campaigns. The 1st campaign was carried out over three days in the winter 2020; the 2nd one was held over three days in the summer 2021. Three collocated stations equipped with u-blox ZED F9P receivers and one station with a high-grade Trimble Alloy receiver were used. Receivers were connected to two different types of GNSS antennas: a surveying-grade Leica AR10 and a patch ANN-MB antenna. Collected GNSS data were processed using Bernese GNSS Software v.5.2 in Precise Point Positioning (PPP) mode based on dual-frequency ionosphere-free model.

The presented results confirm that the tropospheric solutions based on low-cost receivers data can achieve high accuracy. Low-cost equipment provides tropospheric parameters with precision and reliability only slightly lower than that of high-grade one. We also show that an application of a surveying-grade antenna to a low-cost receiver may noticeably enhance the accuracy of the tropospheric estimates derived with such receivers. Finally, validation against the ERA5 climate reanalysis confirms that both sets can provide high-quality, accurate tropospheric estimates, which can be further used in climate applications.

How to cite: Stępniak, K. and Paziewski, J.: Validation of low-cost receiver derived tropospheric products against ERA5 reanalysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7899, https://doi.org/10.5194/egusphere-egu22-7899, 2022.

09:55–10:00
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EGU22-8242
|
Virtual presentation
Raphael Stauffer, Roland Hohensinn, Iván Darío Herrera Pinzón, Gregor Möller, and Markus Rothacher

With the introduction of the operating system Android 7 Nougat in the year 2016, it became possible to access the GNSS code and carrier phase observations on Android smartphones. These observations can now be processed with state-of-the-art GNSS processing software, which allows an in-depth evaluation of the smartphone`s GNSS performance. The availability of the carrier phase observations is an important step towards sub-decimeter-level positioning. Since a few years, there are also smartphones on the market that are equipped with dual-frequency GNSS chipsets.

In this presentation, the capability of dual-frequency GNSS smartphones for the estimation of tropospheric delays is investigated. Static measurements over several weeks are performed using a Google Pixel 4 XL smartphone. The measurements are processed using relative positioning methods in a real-time mode, where a Continuously Operating Reference Station (CORS) acts as a base. The estimated differential tropospheric parameters – derived for short and medium baseline lengths – are then added to the absolute values computed at the reference station by Precise Point Positioning (PPP). Using this method, we demonstrate that the tropospheric zenith total delays can be successfully determined from smartphone observations. When comparing the estimated tropospheric delays with those determined at a nearby geodetic receiver, differences in the range of a few millimeters to centimeters are visible. In view of these accuracies, the suggested method shows the potential to resolve small-scale tropospheric structures and thus, can be an interesting data source for numerical weather prediction models or related GNSS crowdsourcing projects.

How to cite: Stauffer, R., Hohensinn, R., Herrera Pinzón, I. D., Möller, G., and Rothacher, M.: Tropospheric Parameter Estimation with Dual-Frequency GNSS Smartphones, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8242, https://doi.org/10.5194/egusphere-egu22-8242, 2022.

Coffee break
Chairpersons: Jacek Paziewski, Felix Perosanz, Elisa Benedetti
10:20–10:25
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EGU22-11197
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ECS
|
On-site presentation
Kamil Kazmierski, Marcin Mikos, and Natalia Wachulec

It is difficult to imagine today's world without Global Navigation Satellite Systems (GNSS). The dynamic development of GNSS has contributed to the fact that current users are able to use four global systems that use more than 120 satellites. This progress was related not only to the space segment but also to the user segment. Modern technology and miniaturization have resulted in the users' disposal of different types of GNSS receivers, including geodetic receivers, gaining popularity low-cost receivers, or other devices using the GNSS signal, such as smartphones, sports trackers, or sports watches.

Modern sports watches are equipped with many sensors, among which GNSS chipsets play an important role. Those GNSS chipsets make it possible to determine the distance traveled and other related parameters that are important from the point of view of athletes. The most modern constructions can track several constellations at the same time. However, it is difficult to find reliable information to determine the actual quality of positioning by these low-cost GNSS receivers. Most of the works use comparative methods of watches and visual analysis of the route covered. Due to the above-mentioned gap in this area, the positioning quality of leading manufacturers of sports watches was assessed in this study.

Ten sports watches from Garmin, Polar, and Suunto were assessed in the study regarding the geodetic grade GNSS Trimble receiver. The watches were evaluated in three experiments: field positioning experiment, distance accuracy experiment conducted on the athletics track, and the accuracy of the altitude determination conducted on the 37 m high tower. The tests were performed for all the GNSS system options available in watches. The best positioning quality was obtained for the Polar M430 watch that uses only GPS for which almost all recorded epochs obtain positioning accuracy better than 5 m. When measuring distance, most watches had a result that was less than 1% from the theoretical value. Garmin Vivoactive 4s achieved the best results in height determination. For 11 different measured levels, located about 3 m apart, it obtained an average difference equal to 0.48 m. The results show also that the use of the additional GNSS system degrades the obtained results in some cases.

How to cite: Kazmierski, K., Mikos, M., and Wachulec, N.: Evaluation of positioning accuracy with the use of sports watches equipped with GNSS modules, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11197, https://doi.org/10.5194/egusphere-egu22-11197, 2022.

10:25–10:30
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EGU22-9079
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ECS
|
Presentation form not yet defined
|
Roland Hohensinn, Raphael Stauffer, Iván Darío Herrera Pinzón, Gregor Möller, Matthias Aichinger-Rosenberger, Yara Rossi, Yuanxin Pan, Grzegorz Kłopotek, Benedikt Soja, and Markus Rothacher

In recent years, dual-frequency GNSS chipsets became available on the mass market. The ongoing developments in sensor and processing technologies steadily improve the positioning performance so that nowadays sub-decimeter accuracies can be achieved with such devices, even in real-time. Thus these sensors become a powerful, inexpensive choice for equipping or densifying existing GNSS monitoring networks. Station densification can be of significant added value for earthquake early warning systems, assimilation of GNSS water vapor estimates into numerical weather prediction models and the detection of severe weather events. Even if somewhat noisier, smartphone data can be used for GNSS-based remote sensing purposes as well.

This contribution is twofold, and focusses on both, the current capabilities and the perspectives of these GNSS low-cost technologies for such remote sensing applications. In the first part we highlight the accuracy of PPP-enabled seismic and tropospheric monitoring using low-cost loggers and stations developed in-house. We show that differential smartphone GNSS observations on short- and medium-length baselines can be used to sense the state of the regional troposphere. In the second part, we present first results on the performance of the u-blox D9S application board, which enables highest precision by PPP-RTK with ambiguity resolution, and the feasibility of high-precision positioning is assessed for long baselines involving smartphone data as well. Finally, we briefly discuss the potential of data-driven methods for mitigating multipath, which is still one of the main error sources when using equipment of low quality. Concerning the GNSS processing, we rely on further-developed versions of open-source and commercial GNSS software packages. Regarding sensor technology, u-blox chips -- which are currently deployed in our self-sufficient GNSS stations -- are used together with different low-cost and medium-grade GNSS antennas (both, patch and recent helical-type low-cost antennas).

We conclude that low-cost GNSS sensor technology is on the way to satisfy the same demands in accuracy as geodetic-grade equipment -- centimeter-level accuracy can be obtained, even in real-time. New possibilities for station densifications arise by employing low-cost, autonomous stations or by crowdsourcing of GNSS data with smartphones. These observations can aid in resolving small-scale structures in the atmosphere, or for a quick detection and localization of geohazards.

How to cite: Hohensinn, R., Stauffer, R., Herrera Pinzón, I. D., Möller, G., Aichinger-Rosenberger, M., Rossi, Y., Pan, Y., Kłopotek, G., Soja, B., and Rothacher, M.: Low-cost and smartphone GNSS sensors: current capabilities and perspectives for seismic and tropospheric monitoring applications, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9079, https://doi.org/10.5194/egusphere-egu22-9079, 2022.

10:30–10:35
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EGU22-2512
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ECS
|
On-site presentation
Lavinia Tunini, David Zuliani, and Andrea Magrin

The global data coverage of the Global Navigation Satellite Systems (GNSS) provides a fundamental and unique dataset for a wide range of applications, such as crustal deformation, topographic measurements, or near surface processes studies. However, a strong limitation is represented by the high costs of the GNSS receivers and the supporting software, which make them available only by the scientific communities capable of affording them. The GNSS technology has been continuously and rapidly growing and, in recent years, new cost-efficient (low-cost) instruments have entered the mass market, gaining the attention of the scientific community for potentially being high-performing alternative solutions. In this study, we matched in parallel a dual-frequency cost-effective receiver (u-blox ZED F9P) and two high-cost receivers, all connected to the same geodetic-class antenna. We tested the system by processing the data together with the observations coming from a network of GNSS permanent stations operating in North-East Italy. We compare the time-series obtained using cost-effective geodetic equipment with those obtained using geodetic-class instruments. We show that mm-order precision can be achieved by cost-effective GNSS receivers, while the results in terms of time series are largely comparable to those obtained using high-price geodetic receivers.

How to cite: Tunini, L., Zuliani, D., and Magrin, A.: Cost-effective GNSS sensors applied for crustal deformation purposes: insights from an experiment in NE-Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2512, https://doi.org/10.5194/egusphere-egu22-2512, 2022.

10:35–10:40
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EGU22-13439
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Virtual presentation
|
Michela Ravanelli, Federico Ferrara, Federica Fuso, Andrea Cannata, Mattia Crespi, and Giovanni Occhipinti

The 2022 Tonga event highlight the necessity to have more and more knowledge about the activity
of volcanoes. To this point, it is well known that volcanoes explosion can trigger ionospheric
perturbation detectable through the Global Navigation Satellite System (GNSS) signal [1].

The VARION (Variometric Approach for Real-Time Ionosphere Observation) algorithm has been
successfully applied to detection of ionospheric perturbations in several real-time scenarios [2, 3].
VARION, thus, estimates sTEC (slant total electron content) variations starting from the single time
differences of geometry-free combinations of GNSS carrier-phase measurements.

The aim of this work is to analyse some Etna explosions occurred in 2021 with the VARION algorithm
in order to better study the coupling between volcanoes and ionosphere. This study can pave the
way to a real-time ionospheric monitoring of Etna volcano.

[1] Manta, Fabio, et al. "Correlation between GNSS‐TEC and eruption magnitude supports the use
of ionospheric sensing to complement volcanic hazard assessment." Journal of Geophysical
Research: Solid Earth 126.2 (2021): e2020JB020726.

[2] Ravanelli, Michela, et al. "GNSS total variometric approach: first demonstration of a tool for
real-time tsunami genesis estimation." Scientific Reports 11.1 (2021): 1-12.

[3] Savastano, Giorgio, et al. "Advantages of geostationary satellites for ionospheric anomaly
studies: Ionospheric plasma depletion following a rocket launch." Remote Sensing 11.14 (2019):
1734.

How to cite: Ravanelli, M., Ferrara, F., Fuso, F., Cannata, A., Crespi, M., and Occhipinti, G.: The VARION approach to volcanoes: case study on 2021 Etna eruptions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13439, https://doi.org/10.5194/egusphere-egu22-13439, 2022.

10:40–10:45
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EGU22-13326
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ECS
|
Virtual presentation
Mehmet Bak and Rahmi Nurhan Celik

Deformation measurements and deformation analysis are important fields of study in geodesy. Investigating the results obtained from the deformation analysis is very important for human safety. By monitoring the movements of the earth's crust or engineering structures, many measures can be taken to protect human life against potential disasters. For this reason, geodetic measurement techniques have been used since the beginning of the 20th century. Important studies have been carried out, especially with the development of GNSS measurement techniques for monitoring displacement movements and deformations. Both academic and commercial software are available for deformation analysis for the determination of earth crust movements. However, the increasing interest in studying crustal movements has revealed new demands. Today, developing technology has allowed the development of new platforms for deformation analysis.

In this study, an open source web-based deformation analysis platform named Web-NDefA (Web-'N'etwork 'Def'ormation 'A'nalysis), which was developed for 3D static deformation analysis using geodetic methods, is introduced. In addition, the analysis of a data group obtained from Continuously Operating Reference Stations in the Marmara Region with this platform is also explained. After the processing of the base vectors obtained from univariant GNSS networks with the LGO (Leica Geo Office) software, Web-NDefA is used to load the ASCII file of the base solutions to the platform, to adjust the measurements according to the free adjustment method, to obtain the confidence criteria and to analyse the networks compared according to the static deformation model and S-Transformation method. It is a static deformation analysis platform that performs 3-Dimensional statistical analysis that provides visualization, computation of coordinate differences, and drawing velocity vectors. This platform is written with client-side programming languages. HTML (HyperText Markup Language), CSS (Cascading Style Sheets), JavaScript applications were made.

As a result, in this study, information about the design of the have developed open source web platform is given and GNSS data obtained from certain days in 2016, 2019 and 2020 in the Marmara Region are analysed. In this way, a new vision is put forward to the applications used in GNSS-based static deformation analysis and experts who are interested in monitoring and analysing deformations can access such platforms more easily.

How to cite: Bak, M. and Celik, R. N.: A Web Based Open Source Deformation Analysis Platform for identifying Crustal Movements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13326, https://doi.org/10.5194/egusphere-egu22-13326, 2022.

10:45–10:50
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EGU22-4881
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ECS
|
Virtual presentation
|
Giulio Tagliaferro

Ambiguity fixing on the geometry free combination presents some desirable characteristics. In particular, it does not require precise ephemeris, modelling of station displacement motion or tropospheric modelling or estimation. For such reasons, it can be particularly interesting in the case where such data and models are not available or if simpler processing is wanted. Such fixing procedure has been studied in the past for dual-frequency and triple frequency cases. Unfortunately, especially in the two frequency case, this procedure is not practical due to the long observation period needed to reliable fix a correct integer set. In this contribution, we review the fixing performances of the “geometry free” model using an undifferenced uncombined approach. Furthermore, we present the case to four and five frequency cases using Galileo and Beidou observations showing that reliable fixing in a reduced time span is possible. All analyses presented are performed using real GNSS data from the IGS permanent network. Finally, some possible applications are presented with a focus on ionospheric studies.

How to cite: Tagliaferro, G.: Ambiguity fixing on geometry free like model using modernized GNSS signals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4881, https://doi.org/10.5194/egusphere-egu22-4881, 2022.

10:50–10:55
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EGU22-2327
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ECS
|
On-site presentation
|
Radosław Zajdel, Kamil Kazmierski, and Krzysztof Sośnica

Global Navigation Satellite Systems (GNSSs) are widely used for Earth system monitoring, e.g., solid earth and atmosphere. However, the time series of station coordinates and zenith tropospheric delay derived using GNSS are inherently affected by several technique-specific errors that influence the interpretation of geophysical processes and phenomena. GPS plays a crucial role and is most often used in interdisciplinary studies. However, the multiplicity of navigation systems, including fully operational GLONASS and Galileo, allowed us to assess system-specific high-frequency signals and inconsistencies arising from using different constellations.

This work shows that using different GNSS constellations leads to the appearance of various artificial signals with amplitudes up to several millimeters in the series of station coordinates. The presence of the GNSS system-specific artifacts and inter-system disagreements are demonstrated using the 2-year long series of station coordinates and zenith total delay parameters for 15 stations using Precise Point Positioning algorithms. Finally, we assessed the benefit of using GPS, GLONASS, and Galileo jointly.

We identified the origin of the spurious signals in orbital errors. The most dominant orbital artifacts for Galileo appear with periods of 14.08 h, 17.09 h, 34.20 h, 2.49 d, ~3.4 d. The corresponding signals for GLONASS appear with periods of 5.63 h, 7.36 h, 10.64 h, 21.26 h, 3.99 d, and ~8 d. Moreover, when estimating discrete 24-hour solutions from high-rate GNSS data, high-frequency signatures are under-sampled, resulting in long-term aliased periodic signals. The GPS orbital signals arise at the periods corresponding to the harmonics of the K1 tide, which leads to the inconsistency of the GPS-based products with ocean tidal loading models reaching on average 12 mm for the K2 tidal term in the Up component. The magnitude of the orbital signals varies between different site locations and depends on the GNSS observation geometry and dominant direction of satellites' flybys. For example, because of the high inclination of the GLONASS orbital planes, the stations located in absolute low latitudes observe mostly North-South satellite flybys; thus, the estimated East component of the coordinates is exposed to the orbital artifacts.

Galileo is less vulnerable to the orbital signals than GPS or GLONASS. The difference is visible mainly for the East coordinate component. The Galileo-based daily estimates are up to 55% and 36% better than those delivered from GLONASS and GPS. Finally, using a combination of GPS and Galileo increases the precision of estimates by 10% compared with the best-case Galileo-only solution and remarkably reduces the system-specific errors in station coordinate time series.

How to cite: Zajdel, R., Kazmierski, K., and Sośnica, K.: Inconsistency in Precise Point Positioning products from GPS, GLONASS and Galileo , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2327, https://doi.org/10.5194/egusphere-egu22-2327, 2022.

10:55–11:00
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EGU22-7489
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ECS
|
Presentation form not yet defined
|
Damian Kiliszek, Andrzej Araszkiewicz, and Krzysztof Kroszczyński

At present, significant development of the positioning methods using the Global Navigation Satellite System (GNSS) can be seen. One of the most developed methods is the absolute Precise Point Positioning (PPP) method. This can be particularly seen using multi-GNSS measurements. The development of multi-GNSS increases the number of satellites observed and increases the accuracy of the products, but also creates new requirements for observation modeling. Obtaining the correct values, ​​of the estimated parameters, requires the appropriate determination of the deterministic model as well as the stochastic model. Currently, the deterministic model is well known. In contrast, the stochastic model is not fully known and still requires a number of studies. Stochastic modeling is based on determining the covariance matrix and which can be modeled using a weighting function that takes into account the elevation angle of the observed satellite. ​

In our analysis, we focus on studies on the weighting functions of GNSS observations for the PPP method. Analysis was performed on the Multi-GNSS Pilot Project (MGEX) stations which were characterized by global distribution and various equipment in 2021. Studies were conducted for the GPS‑only, Galileo-only, and GPS+Galileo constellations, with particular emphasis on the Galileo observations, which has achieved significant progress in recent years. Eight different observation weighting models have been selected for analysis: one of them assumes that all observations have the same precision, without dependence on the elevation angle; for the other used functions, the observation precision value depends on the elevation angle. Parameters such as accuracy, convergence time, zenith path delay (ZPD), and inter-system bias (ISB) are analyzed.

Based on the tests performed, we show that, depending on the solutions adopted (i.e. GPS-only, Galileo-only, GPS+Galileo), the best results were obtained for different weighting functions. We have shown that using different weighting functions have no impact on the horizontal component but a visible impact on the vertical component,  the tropospheric delay, and the convergence time. Also, we choose the best functions for GPS-only and Galileo-only and used them for the GPS+Galileo solution. For this new approach obtained a shorter convergence time and higher accuracy of the ZPD. More information and results will be presented at the conference.

How to cite: Kiliszek, D., Araszkiewicz, A., and Kroszczyński, K.: Analysis of different weighting functions of observations for GPS and Galileo PPP, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7489, https://doi.org/10.5194/egusphere-egu22-7489, 2022.

11:00–11:05
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EGU22-12926
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ECS
|
Virtual presentation
|
Robert Galatiya Suya, Yung-Tsang Chen, Chiew-Foong Kwong, and Penghe Zhang

The use of theoretical modeling algorithms to compute the satellite altitude causes some errors which are eventually absorbed by the satellite clocks. This adversely reduces the fixed positioning performance in global navigation satellite system (GNSS) precise point positioning (PPP). Currently, different International GNSS service (IGS) analysis centers (ACs) provide satellite altitude quaternions which are an auxiliary dataset necessary in PPP fixed solutions. Hence, this study aims at a comprehensive evaluation of the effect of accounting for the BeiDou satellite attitude quaternions in PPP. The quaternions provided by different ACs are applied to BeiDou PPP using different weighting schemes suitable for handling satellites in three distinct orbits. The obtained numerical results indicate that considering the quaternions in BeiDou PPP reduces the observation residuals, improves the ambiguity fixing, and enhances positioning performance.

How to cite: Suya, R. G., Chen, Y.-T., Kwong, C.-F., and Zhang, P.: Considering Satellite Attitude Quaternions in BeiDou Precise Point Positioning Performance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12926, https://doi.org/10.5194/egusphere-egu22-12926, 2022.

11:05–11:10
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EGU22-7927
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ECS
|
Virtual presentation
|
Fikri Bamahry, Juliette Legrand, Carine Bruyninx, and Andras Fabian

The European Plate Observing System (EPOS) is a very large and complex European e-infrastructure that provides pre-operational access to a first set of datasets and services for Solid Earth research. The EPOS-GNSS Data Gateway provides, through an Application Program Interface (API) and a web portal, access to GNSS (Global Navigation Satellite Systems) RINEX data from a distributed infrastructure of data nodes. Currently, ten EPOS-GNSS nodes have been installed, and three of them are still in the pre-operational phase. To monitor the long-term data quality of EPOS-GNSS stations at the nodes level, ROB is developing a new service. The first step of this service is a web portal (www.gnssquality-epos.oma.be) that provides access to data quality metrics of the RINEX data available from the different EPOS-GNSS nodes.

The web portal presents plots of the long-term tracking performance of more than 1000 EPOS-GNSS stations. The plots focus on several data quality metrics such as the number of observed versus expected observations, the number of missing epochs, the number of observed satellites, the number of cycle slips, and multipath values on code observations. These metrics have been computed at the node level using GLASS and Anubis Software (https://gnutsoftware.com/software/anubis). The metrics provide helpful information for node managers or station users to assess the EPOS-GNSS station’s performance and detect potential degradation of the RINEX data quality. The outlook of this work is to investigate the possible usage of data quality metrics to detect data unsuitable for high-precision GNSS analysis for geophysical or meteorological applications. Here, we will present the newly developed web portal, the considered data quality metrics, and some preliminary results of this ongoing work.

How to cite: Bamahry, F., Legrand, J., Bruyninx, C., and Fabian, A.: First experience with GNSS data quality monitoring in the distributed EPOS e-infrastructure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7927, https://doi.org/10.5194/egusphere-egu22-7927, 2022.

11:10–11:15
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EGU22-8890
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Virtual presentation
Deniz Cetin, D.Ugur Sanli, and Sermet Ogutcu

For a long time, the main factor affecting the accuracy of GPS PPP has been the observing session duration. Researchers have recently shown that the accuracy of PPP also varies with latitude. The reason for the latitudinal variation is the inability to determine the tropospheric zenith delay with a globally homogeneous precision and its impact on the position determination results. A formula has been developed to give the accuracy of the PPP position in a local geocentric system based on observation session duration and latitude. Currently, the interest of researchers is to determine the accuracy of Multi-GNSS solutions. In this context, the MGEX experiment of the IGS provides a rich data source to researchers. In this study, 15 globally distributed GNSS stations were selected from the MGEX network, GPS+GLONASS data was evaluated with CSRSPPP software, and the accuracy of the GNSS positioning was investigated. Continuous GNSS observations and 8-hour campaign measurements are evaluated comparatively. The results of the study showed that 60% of the RMS values obtained from the 24-hour data became smaller, indicating that it was equal between the horizontal and vertical coordinate components. The improvement in campaign solutions is better and around 80% overall. The share of this between horizontal position and vertical position is around 73% and 87%, respectively. The average improvement in the RMS of the coordinate components is around 0.5 mm for the campaign solutions, but the improvement can reach up to 2 mm at some stations. Our motivation was to determine whether this improvement was reflected in the accuracy modeling. Initial findings show that the results are in agreement with the latest accuracy modeling, and it turns out that the positioning accuracy of GNSS PPP also depends on the latitude of the GNSS site as well as the observation session, as in the GPS PPP.

How to cite: Cetin, D., Sanli, D. U., and Ogutcu, S.: Accuracy of GNSS positioning: GPS+GLONASS case, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8890, https://doi.org/10.5194/egusphere-egu22-8890, 2022.