A prototype for a Multi-GNSS orbit combination

Sakic, Pierre; Mansur, Gustavo; Männel, Benjamin

doi:10.31223/osf.io/kxqsc

Cited by 3 publications

(5 citation statements)

References 3 publications

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“…QZSS shows the highest RMS values, which can reach around 80 mm. This behavior is also noted by Sakic et al [2020] who used an adaptation of the IGS legacy software to process the MGEX orbits. Similar results are provided by the ACC where another adaptation of the legacy software is used 4 .…”

Section: Differences Between Individual Ac Orbit Solutions and Combinsupporting

confidence: 52%

“…The GFZ IGS working group has also been putting efforts to study and provide a dedicated and entirely consistent orbit and clock combination using the solutions provided by the ACs that contribute to the MGEX project. Previous studies were made adapting the IGS combination software [Fritsche, 2016;Mansur et al, 2020;Sakic et al, 2020], and have shown that significant modifications are needed to combine MGEX products, including an improved weighting strategy adapted to the different constellations. Therefore, only an adaptation of the existing software may not be enough to handle the different constellations with different quality of orbit solutions, as well as may not provide a full perspective about the influence that each AC has on a specific constellation.…”

Section: Introductionmentioning

confidence: 99%

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Combination of GNSS orbits using variance component estimation

Mansur¹,

Sakic²,

Brack³

et al. 2023

Preprint

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Over the past years, the International GNSS Service (IGS) has been putting efforts into extending its service towards the Multi-GNSS Experiment and Pilot Project (MGEX). Several MGEX Analysis Centers (ACs) contribute by providing solutions containing not only GPS and GLONASS but also Galileo, BeiDou, and QZSS. The MGEX orbit and clock combination is a product that is still not consolidated inside the IGS and requires studies in order to provide a consistent solution. In this contribution, we present a least-squares framework for a multi-GNSS orbit combination, where the weights used to combine the ACs' orbits are determined by least-squares variance component estimation. We introduce and compare two weighting strategies, where either AC specific weights or AC and constellation specific weights are used. Both strategies are tested using MGEX orbit solutions for a period of two and a half years. They yield similar results with an agreement with the ACs' orbits at the one centimeter level for GPS and up to a few centimeters for the other constellations. The agreement is generally slightly better with the AC and constellation weighting. A comparison of our combination approach with the official combined IGS final solution using three years of GPS, and GLONASS orbits from the regular IGS processing shows an agreement of better than 5 mm and 12 mm for GPS and GLONASS, respectively. An external validation using Satellite Laser Ranging (SLR) is performed for our combined MGEX orbit solutions with both weighting schemes.

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Section: Differences Between Individual Ac Orbit Solutions and Combinsupporting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Combination of GNSS orbits using variance component estimation

Mansur¹,

Sakic²,

Brack³

et al. 2023

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…This algorithm can also handle the different constellations separately. It corrects the weaknesses of the legacy software used routinely by the IGS's ACC, which have been raised during a preliminary study investigating the possibilities to improve it for a multi-GNSS environment (Sakic et al 2020). We tested this new algorithm with the recent set of orbit products generated by the different IGS ACs in the framework of the repro3 reprocessing campaign.…”

Section: Discussion and Perspectivesmentioning

confidence: 99%

“…Thus, our research group has started to study a new combination strategy compatible with the new constellations, initially based on the legacy IGS software (Sakic et al 2020), then by designing an ad hoc strategy optimised for a multi-GNSS configuration (Mansur et al 2020b,a). These activities are carried out in parallel with the orbit combination studies performed by the ACC in the context of the IGS's Multi-GNSS Experiment (MGEX) pilot project (Sośnica et al 2020), and the ones regarding integer clocks (Banville et al 2020).…”

Section: Introductionmentioning

confidence: 99%

An Experimental Combination of IGS repro3 Campaign’s Orbit Products Using a Variance Component Estimation Strategy

Sakic

Mansur

Männel

et al. 2022

International Association of Geodesy Symposia

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Over the past years, the International GNSS Service (IGS) has put efforts into reprocessing campaigns, reanalyzing the entire data collected by the IGS network since 1994. Using state-of-the-art models and software, the goal is to provide a consistent set of orbits, station coordinates, and earth rotation parameters. Unlike the previous campaigns—namely: repro1 and repro2—, the repro3 includes not only GPS and GLONASS but also the Galileo constellation. The main repro3 objective is the contribution to the next realization of the International Terrestrial Reference Frame (ITRF2020). To achieve this goal, several Analysis Centers (AC) submitted their own products to the IGS, which are combined to provide the final solutions for each product type. In this contribution, we focus on the combination of the orbit products. We present a consistent orbit solution based on a newly developed combination strategy, where the weights are determined by a Least-Squares Variance Component Estimation (LSVCE). The orbits are intended to be combined in an iterative processing: firstly, by aligning all the products via a Helmert transformation, secondly by defining which satellites will be used in the LSVCE, and finally by normalizing the inverse of the variances as weights that are used to compute a weighted mean. The combination results show an agreement between the different AC’s input orbits around 10 mm for GPS, 30 mm for GLONASS. The combination also highlights the improvement of the Galileo orbit determination over the past decade, the internal precision decreasing from around 35 mm to 16 mm for the most recent weeks. We used Satellite Laser Ranging (SLR) observations for external validation. The combined orbit has one of the best RMS agreements with respect to the SLR measurements (9.1 mm for GLONASS, and 8.3 mm over the last five years of the processed period).

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“…For the combined solution of multi-GNSS orbits, two alignment methods of the orbits to ITRF using ERP and individual orbit/station coordinates, respectively, which initially obtained IGS combined multi-system orbit products [14,15]. However, in that study, all systems were treated as a whole for orbit combination, and the differences of product frame and orbit accuracy between different analysis centers or systems were ignored, maybe resulting in unreasonable weight distribution of ACs.…”

Section: Introductionmentioning

confidence: 99%

Multi-GNSS Combined Orbit and Clock Solutions at iGMAS

Zhou¹,

Cai²,

Chen

et al. 2022

Sensors

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Global navigation services from the quad-constellation of GPS, GLONASS, BDS, and Galileo are now available. The international GNSS monitoring and assessment system (iGMAS) aims to evaluate the navigation performance of the current quad systems under a unified framework. In order to assess impact of orbit and clock errors on the positioning accuracy, the user range error (URE) is always taken as a metric by comparison with the precise products. Compared with the solutions from a single analysis center, the combined solutions derived from multiple analysis centers are characterized with robustness and reliability and preferred to be used as references to assess the performance of broadcast ephemerides. In this paper, the combination method of iGMAS orbit and clock products is described, and the performance of the combined solutions is evaluated by various means. There are different internal precisions of the combined orbit and clock for different constellations, which indicates that consistent weights should be assigned for individual constellations and analysis centers included in the combination. For BDS-3, Galileo, and GLONASS combined orbits of iGMAS, the root-mean-square error (RMSE) of 5 cm is achieved by satellite laser ranging (SLR) observations. Meanwhile, the SLR residuals are characterized with a linear pattern with respect to the position of the sun, which indicates that the solar radiation pressure (SRP) model adopted in precise orbit determination needs further improvement. The consistency between combined orbit and clock of quad-constellation is validated by precise point positioning (PPP), and the accuracies of simulated kinematic tests are 1.4, 1.2, and 2.9 cm for east, north, and up components, respectively.

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A prototype for a Multi-GNSS orbit combination

Cited by 3 publications

References 3 publications

Combination of GNSS orbits using variance component estimation

Combination of GNSS orbits using variance component estimation

An Experimental Combination of IGS repro3 Campaign’s Orbit Products Using a Variance Component Estimation Strategy

Multi-GNSS Combined Orbit and Clock Solutions at iGMAS

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