A prototype for a Multi-GNSS orbit combination

Sakic, Pierre; Mansur, Gustavo; Männel, Benjamin

doi:10.23919/enc48637.2020.9317316

Cited by 9 publications

(4 citation statements)

References 20 publications

(19 reference statements)

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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 combine 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 Combin...supporting

confidence: 53%

“…The GFZ IGS team has been putting efforts to study and provide a dedicated and entirely consistent orbit and clock combination using the solutions provided by the ACs contributing 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. In the current software, the combination for GPS and GLONASS is done completely independent for each constellation, which is not ideal in terms of interoperability.…”

Section: Introductionmentioning

confidence: 99%

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Combination of GNSS orbits using least-squares variance component estimation

Mansur

Sakic

Brack

et al. 2022

J Geod

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Over the past years, the International GNSS Service (IGS) has been putting efforts into extending its service by setting up and running 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. As the current IGS combination software can only handle the orbits of one constellation at a time, it requires substantial modifications to obtain a consistent MGEX orbit product. 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. An automated Z-score test is implemented yielding a common set of core satellites that are used to determine the weights. 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 3D-RMS is generally slightly better with the AC and constellation weighting. A comparison of our combination approach with the official IGS combination using three years of GPS and GLONASS orbits shows an agreement of better than 5 mm and 12 mm for GPS and GLONASS, respectively, while the agreement of the official IGS combination with the ACs’ GPS solutions is only around $$15\,\textrm{mm}$$ 15 mm . An external validation using satellite laser ranging shows that the mean residuals of our combined products are around $$-3\,\textrm{mm}$$ - 3 mm for Galileo, $$6\,\textrm{mm}$$ 6 mm for GLONASS, $$-8\,\textrm{mm}$$ - 8 mm for BeiDou, and $$-31\,\textrm{mm}$$ - 31 mm for QZSS.

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Section: Differences Between Individual Ac Orbit Solutions and Combin...supporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Combination of GNSS orbits using least-squares variance component estimation

Mansur

Sakic

Brack

et al. 2022

J Geod

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“…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). 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).…”

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confidence: 99%

An experimental combination of IGS repro3 campaign’s orbit products using a variance component estimation strategy

Sakic¹,

Mansur²,

Männel³

et al. 2023

Preprint

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Over the past years, the International GNSS Service (IGS) has put efforts into reprocessing campaigns reanalyzing the full data collected by the IGS network since 1994. The goal is to provide a consistent set of orbits, station coordinates, and earth rotation parameters using state-of-the-art models. Different from 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 specific products, 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 will 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 combined in an iterative processing, first aligning all the products via a Helmert transformation, second defining which satellites will be used in the LSVCE, and finally normalizing the inverse of the variances as weights that are used to compute a weighted mean. Moreover, we will discuss the weight factors and their stability in the time evolution for each AC depending on the constellations. In addition, an external validation using a Satellite Laser Ranging (SLR) procedure will be shown for the combined solution.

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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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A prototype for a Multi-GNSS orbit combination

Cited by 9 publications

References 20 publications

Combination of GNSS orbits using least-squares variance component estimation

Combination of GNSS orbits using least-squares variance component estimation

An experimental combination of IGS repro3 campaign’s orbit products using a variance component estimation strategy

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

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