Radar Corner Reflector installation at the OCA geodetic Observatory (France)

2020 ◽  
Author(s):  
Xavier Collilieux ◽  
Clément Courde ◽  
Bénédicte Fruneau ◽  
Mourad Aimar ◽  
Guillaume Schmidt ◽  
...  
Keyword(s):  
Reference System ◽  
Satellite System ◽  
Corner Reflector ◽  
Combination Process ◽  
Long Baseline ◽  
Space Geodetic Techniques ◽  
Gnss Permanent Stations ◽  
The Stability ◽  
Global Navigation Satellite ◽  
Ground Displacements

<p>Geodetic observatories play a fundamental role in the determination of the International Terrestrial Reference System releases. They host several geodetic permanent instruments whose coordinates can be determined at the centimeter level or better. They comprise Global Navigation Satellite System (GNSS) permanent antenna/receivers, Satellite Laser Ranging (SLR) stations, Very Long Baseline Interferometry (VLBI) telescope and Doppler Orbitography Integrated by Satellite (DORIS) beacons. The Calern site of the Observatoire de la Côte d’Azur (OCA) is an example of such a multi-technique site located in the South of France. It hosts a DORIS beacon, a SLR/LLR station and two GNSS permanent stations.</p><p> </p><p>In the process of determining coordinates of geodetic instruments in a unified reference frame, the relative positions of the instruments at co-location sites are integrated in the ITRF combination. Thanks to the additional measurements obtained from local surveys, it is possible to determine global biases between coordinates determined by individual space geodetic techniques, and express them in the same reference system. An additional fundamental assumption of the combination process is that stations located on the same site do not move with respect to each other. Spaceborne Synthetic Aperture Radar Interferometry (INSAR technique), is an interesting tool to evaluate that hypothesis as it allows measuring ground displacements in the line of sight of the satellite,  and has been used only occasionally in the past for this purpose,. Notably, the Persistent Scatterer (PS) Interferometry enables determining time series of ground displacements on particular scatterers exhibiting phase stability in a stack (or series ?) of SAR images. To ensure the existence (or presence ?) of such PS, artificial corner reflectors can be installed.</p><p> </p><p>We present the procedure that we adapted from Parker et al. (2007) to install and validate the installation of a corner reflector at OCA observatory, close to the currently operating GNSS, SLR and DORIS stations, specifically designed for Sentinel-1 satellite. An initial local tie survey was carried out to assess the stability of the reflector through time.</p>

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

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Jin Wang ◽  
Qin Zhang ◽  
Guanwen Huang
Keyword(s):  
Estimation Method ◽  
Satellite Orbit ◽  
Satellite System ◽  
Assessment System ◽  
Navigation Satellite ◽  
Dual Frequency ◽  
Fractional Cycle Bias ◽  
The Stability ◽  
High Consistency ◽  
Global Navigation Satellite

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

scholarly journals Modeling and Analysis of BDS-2 and BDS-3 Combined Precise Time and Frequency Transfer Considering Stochastic Models of Inter-System Bias

2021 ◽  
Vol 13 (4) ◽  
pp. 793
Author(s):  
Guoqiang Jiao ◽  
Shuli Song ◽  
Qinming Chen ◽  
Chao Huang ◽  
Ke Su ◽  
...  
Keyword(s):  
Stochastic Models ◽  
Satellite System ◽  
Modeling And Analysis ◽  
System Bias ◽  
Frequency Transfer ◽  
Global Navigation ◽  
The Difference ◽  
The Stability ◽  
Global Navigation Satellite ◽  
Precise Time

BeiDou global navigation satellite system (BDS) began to provide positioning, navigation, and timing (PNT) services to global users officially on 31 July, 2020. BDS constellations consist of regional (BDS-2) and global navigation satellites (BDS-3). Due to the difference of modulations and characteristics for the BDS-2 and BDS-3 default civil service signals (B1I/B3I) and the increase of new signals (B1C/B2a) for BDS-3, a systemically bias exists in the receiver-end when receiving and processing BDS-2 and BDS-3 signals, which leads to the inter-system bias (ISB) between BDS-2 and BDS-3 on the receiver side. To fully utilize BDS, the BDS-2 and BDS-3 combined precise time and frequency transfer are investigated considering the effect of the ISB. Four kinds of ISB stochastic models are presented, which are ignoring ISB (ISBNO), estimating ISB as random constant (ISBCV), random walk process (ISBRW), and white noise process (ISBWN). The results demonstrate that the datum of receiver clock offsets can be unified and the ISB deduced datum confusion can be avoided by estimating the ISB. The ISBCV and ISBRW models are superior to ISBWN. For the BDS-2 and BDS-3 combined precise time and frequency transfer using ISBNO, ISBCV, ISBRW, and ISBWN, the stability of clock differences of old signals can be enhanced by 20.18%, 23.89%, 23.96%, and 11.46% over BDS-2-only, respectively. For new signals, the enhancements are −50.77%, 20.22%, 17.53%, and −3.69%, respectively. Moreover, ISBCV and ISBRW models have the better frequency transfer stability. Consequently, we recommended the optimal ISBCV or suboptimal ISBRW model for BDS-2 and BDS-3 combined precise time and frequency transfer when processing the old as well as the new signals.

Comparison of Tropospheric Zenith Wet Delay from VLBI and GNSS Estimations

2021 ◽  
Author(s):  
Vicky Jia Liu ◽  
Maaria Nordman ◽  
Nataliya Zubko
Keyword(s):  
Time Series ◽  
Seasonal Variations ◽  
Elevation Angle ◽  
Correlation Coefficients ◽  
Satellite System ◽  
Tropospheric Delay ◽  
Polar Regions ◽  
Long Baseline ◽  
Zenith Wet Delay ◽  
Space Geodetic Techniques

<p>Tropospheric delay is one of the major error sources for space geodetic techniques such as Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite System (GNSS). In this study, we compared the agreement of tropospheric zenith wet delay (ZWD) seasonal variations derived from VLBI and GNSS observations at 8 stations that are located at all around the globe. We have analysed time series of 8 years, starting in 2012 until end of 2019. Results show that VLBI_ZWD present clear seasonal variations which depend on the location of each station, in the tropics the variability is more pronounced than in mid-latitudes or polar regions. Furthermore, the VLBI_ZWD also shows a reasonably good agreement with seasonal fit model. When comparing zenith wet delays derived from co-located GNSS and VLBI stations at  cut-off elevation angle, they agree quite well, which is proved by the high correlation coefficients, varying from 0.6 up to 0.95. The biases between the techniques are in mm level and standard errors of the whole time series are in few centimetres.</p>

Deformation detection through the realization of reference frames

2020 ◽  
Vol 14 (2) ◽  
pp. 133-148
Author(s):  
Nestoras Papadopoulos ◽  
Melissinos Paraskevas ◽  
Ioannis Katsafados ◽  
Georgios Nikolaidis ◽  
Euagelos Anagnostou
Keyword(s):  
Reference Frame ◽  
Reference System ◽  
Reference Frames ◽  
Satellite System ◽  
Geodetic Reference System ◽  
Deformation Model ◽  
Navigation Systems ◽  
International Gnss Service ◽  
Tectonically Active ◽  
Global Navigation Satellite

AbstractHellenic Military Geographical Service (HMGS) has established and measured various networks in Greece which constitute the geodetic infrastructure of the country. One of them is the triangulation network consisting of about 26.000 pillars all over Greece. Classical geodetic measurements that held by the Hellenic Military Geographic Service (HMGS) through the years have been used after adjustment for the state reference frame which materializes the current Hellenic Geodetic Reference System of 1987 (HGRS87). The aforementioned Reference System (RS) is a static one and is in use since 1990. Through the years especially in the era of satellite navigation systems many Global Navigation Satellite System (GNSS) networks have been established. The latest such network materialized by HMGS is ongoing and covers until now more than the 2/3 of the country. It is referenced by International GNSS Service (IGS) permanent stations and consists a local densification IGS08 Reference Frame. Firstly, this gives the opportunity to calculate transformation parameters between the two systems and a statistical analysis of the residuals leads to intermediate conclusions. After that and in conjunction with existing past transformations, tectonic deformations and their directions are concluded. Moreover past GPS observations on the same pillars in compare to the newer ones give also a sense of tectonic displacements. Greece is one of the most tectonically active countries in Europe and the adoption of a modern kinematic or semi-kinematic geodetic datum is a necessity as it should incorporate a deformation model like 3d velocities on the reference frame realization. The detection of geodynamic changes is a continuous need and should be taken into consideration at each epoch.

scholarly journals Fusion of GNSS and Satellite Radar Interferometry: Determination of 3D Fine-Scale Map of Present-Day Surface Displacements in Italy as Expressions of Geodynamic Processes

2019 ◽  
Vol 11 (4) ◽  
pp. 394 ◽  
Author(s):  
Gregorio Farolfi ◽  
Aldo Piombino ◽  
Filippo Catani
Keyword(s):  
Surface Deformation ◽  
Satellite System ◽  
Sar Interferometry ◽  
Ground Movement ◽  
Sight Loss ◽  
Geodynamic Processes ◽  
Ground Point ◽  
Space Geodetic Techniques ◽  
Satellite Radar ◽  
Global Navigation Satellite

We present a detailed map of ground movement in Italy derived from the combination of the Global Navigation Satellite System (GNSS) and Satellite Synthetic Aperture Radar (SAR) interferometry. These techniques are two of the most used space geodetic techniques to study Earth surface deformation. The above techniques provide displacements with respect to different components of the ground point position; GNSSs use the geocentric International Terrestrial Reference System 1989 (ITRS89), whereas the satellite SAR interferometry components are identified by the Lines of Sight (LOSs) between a satellite and ground points. Moreover, SAR interferometry is a differential technique, and for that reason, displacements have no absolute reference datum. We performed datum alignment of InSAR products using precise velocity fields derived from GNSS permanent stations. The result is a coherent ground velocity field with detailed boundaries of velocity patterns that provide new information about the complex geodynamics involved on the Italian peninsula and about local movements.

Determination of global geodetic parameters based on integrated SLR measurements to LEO, geodetic, and Galileo satellites

2020 ◽  
Author(s):  
Dariusz Strugarek ◽  
Krzysztof Sośnica ◽  
Daniel Arnold ◽  
Adrian Jäggi ◽  
Grzegorz Bury ◽  
...  
Keyword(s):  
Precise Orbit Determination ◽  
Satellite System ◽  
Length Of Day ◽  
Long Baseline ◽  
Earth Rotation Parameters ◽  
Gnss Receivers ◽  
Rotation Parameters ◽  
Set Up ◽  
Global Navigation Satellite

<p>Numerous active low Earth orbiters (LEOs) and Global Navigation Satellite System (GNSS) satellites, including the Galileo constellation, are equipped with laser retroreflectors used for Satellite Laser Ranging (SLR). Moreover, most of LEOs are equipped with GNSS receivers for precise orbit determination. SLR measurements to LEOs, GNSS, and geodetic satellites vary in terms of the number of registered normal points (NPs) or registered satellite passes. In 2016-2018, SLR measurements to LEOs constituted 81% of all NPs and 59% of all registered satellite passes, whereas 10% of NPs and 30% of satellite passes, respectively, were assigned to GNSS. The remaining SLR measurements were completed by geodetic satellites, including LAGEOS-1/2, and LARES-1.</p><p>In this study, we show that the SLR observations to Galileo, passive geodetic and active LEO satellites together with precise GNSS-based orbits of LEOs and Galileo, can be used for the determination of global geodetic parameters, such as geocenter coordinates (GCC) and Earth rotation parameters (ERPs), i.e. pole coordinates, and length-of-day parameter.</p><p>GCC are typically determined using SLR observations to passive geodetic satellites, such as LAGEOS-1/2. Also, the SLR observations to LAGEOS-1/2 together with GNSS and Very Long Baseline Interferometry data are used for the determination of ERPs. Here, we use SLR observations to Galileo, LAGEOS-1/2, LARES-1, Sentinel-3A, SWARM-A/B/C, TerraSAR-X, Jason-2, GRACE-A/B satellites to investigate whether they can be applied for the reference frame realization and for deriving high-quality global geodetic parameters.</p><p>We present various types of solutions to investigate the best solution set-up. The studied solutions differ in terms of solution lengths, the combination of different sets of satellites and the relative weights for the variance scaling factors of technique and satellite-specific normal equations. We compare our results with the standard LAGEOS-based solutions, the combined EOP-14-C04 products and show the consistency of the results.</p>

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

2019 ◽  
Vol 12 (1) ◽  
pp. 68 ◽  
Author(s):  
Wang ◽  
Jin ◽  
Yuan ◽  
Hu ◽  
Chen ◽  
...  
Keyword(s):  
Satellite System ◽  
Mean Value ◽  
Systematic Bias ◽  
Navigation Satellite ◽  
Code Bias ◽  
Receiver Dcb ◽  
The Stability ◽  
Global Navigation Satellite ◽  
Academy Of Sciences ◽  
Good Agreement

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

scholarly journals On the modernization of National Geodetic Network with GNSS CORS Reference Frame

2019 ◽  
pp. 28-39
Author(s):  
Sharav Amarjargal ◽  
Gankhuyag Bulgan
Keyword(s):  
Reference Frame ◽  
Crustal Deformation ◽  
Geodetic Network ◽  
Satellite System ◽  
Terrestrial Reference Frame ◽  
National Reference ◽  
Technical Developments ◽  
Tectonically Active ◽  
Space Geodetic Techniques ◽  
Global Navigation Satellite

New technical developments, growing applications and requests for higher accuracy in georeferencing of national reference frame raise a demand on high accuracy National Terrestrial Reference Frame based on Global Navigation Satellite System (GNSS) and other space geodetic techniques. Since the last decades many countries decided to switch main geodetic control points from triangulation points to Continuously Operating Reference Stations (CORS). This task is currently undertaken by the geodetic authority of Mongolia in collaboration with research and private organizations. The first continuous Global Positioning System (GPS) station in Mongolia became operational in the late 1995 for the global geodetic scientific applications. Since 1997 the survey-mode GPS observations were utilized in Mongolia for crustal deformation studies and for re-survey of the national triangulation network. During the years 2011-2013 CORS network of nearly 18 stations has been built to modernize the old geodetic network. Currently the total number of the reference stations counts to nearly 40. Since Mongolia is located in the tectonically active region, its geodetic reference frame is continuously deforming, which requires regular updates of reference frame. In this paper we discuss the technical issues of the national reference frame of Mongolia considering the crustal deformation of Mongolia and the data management of the national CORS network. Үндэсний геодезийн сүлжээг GNSS CORS тулгуур тогтолцоогоор шинэчлэх асуудалд Хураангуй: Техникийн шинэчлэл болон өндөр нарийвчлалтай газарзүйн холболт хийх хэрэгцээ, шаардлагын өсөлт нь Глобаль Навигацийн Дагуулын Систем болон бусад сансрын геодезийн техникт суурилсан илүү өндөр нарийвчлалтай Үндэсний Тулгуур Тогтолцоог шаардах боллоо. Сүүлийн арваад жилд олон улс орон геодезийн хяналтын цэгүүдээ триангуляцийн цэгээс байнгын ажиллагаатай тулгуур станцаар орлуулах үйл ажиллагаа явуулж эхэлсэн бөгөөд хөгжингүй орнууд динамик тогтолцоо руу шилжиж байна. Энэ ажлыг Монгол улсад Газрын Харилцаа Геодези Зурагзүйн Газар толгойлон судалгааны болон хувийн хэвшлийн байгууллагуудтай хамтран хэрэгжүүлж байгаа билээ. Байнгын ажиллагаатай GPS станц Монголд анх 1995 оны сүүлээс ажиллаж эхэлсэн бөгөөд геодезийн шинжлэх ухааны глобаль хэрэглээнд зориулагдаж байв. 1997 оноос эхлэн давтан хэмжилтийн GPS ажиглалтуудыг царцдасын деформац болон триангуляцийн сүлжээг хэмжихэд ашиглаж эхлэв. 2011-2013 оны хооронд триангуляцийн сүлжээг шинэчлэх зориулалтаар ~18 байнгын ажиллагаатай тулгуур станцуудын сүлжээ байгуулагдсан бөгөөд эдгээр станцуудын тоо одоо 40 гарсан байна. Монгол улсын нутаг дэвсгэр нь тектоникийн идэвхтэй бүс нутагт оршдог тул геодезийн тулгуур тогтолцоо нь байнгын деформацд байна. Тиймээс тулгуур тогтолцоог тогтмол шинэчилж байх шаардлагатай. Энэ өгүүлэлд бид үндэсний тулгуур тогтолцооны техник нөхцлийг байнгын ажиллагаатай станцуудын ажиллагаа, Монгол орны царцдасын деформацыг тооцон тусгасан бөгөөд үндэсний CORS (Байнгын Ажиллагаатай Тулгуур Станцын) сүлжээний өгөгдөл, түүний зохицуулалтын талаар илтгэх болно. Түлхүүр үг: GPS геодези, царцдасын деформацын мониторинг, геодезийн сүлжээ

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

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

<p>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.</p><p>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–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 μas 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.</p>

scholarly journals A Robust Method for GPS/BDS Pseudorange Differential Positioning Based on the Helmert Variance Component Estimation

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Jian Deng ◽  
Xingwang Zhao ◽  
Aiguo Zhang ◽  
Fuyang Ke
Keyword(s):  
Real Time ◽  
Variance Component ◽  
Large Deviation ◽  
Satellite System ◽  
Observation Data ◽  
Variance Component Estimation ◽  
Relative Positioning ◽  
Long Baseline ◽  
Component Estimation ◽  
Global Navigation Satellite

The use of global navigation satellite system (GNSS) is entering a new era of joint positioning based on the use of multifrequencies and multimodes. Ensuring the correct weighting of observations from each system and satellite has become a key problem during real-time positioning. This paper addresses the issue of weights of observations as well as the quality control of GPS/BDS pseudoranges in the context of real-time relative positioning. Thus, in the first place, the Helmert variance component estimation (VCE) is used to determine the relative weighting of observations from the two systems, and then, we introduce robustness estimation theory and construct a new method. The method is resistant to the influence of outliers in the observations by selecting weight iterations. To do this, we selected GPS/BDS observation data at baseline lengths of 40 km, 46 km, and 64 km for verification and analysis. Experimental results show that, in terms of the relative positioning of medium-to-long baseline based on GPS/BDS pseudorange observations, when observed values incorporate large gross errors, our method can reduce the weighting of suspicious or abnormal values and weaken their impact on positioning solutions, so that the positioning results will not appear to have large deviation.

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