<div>In the third reprocessing campaign (repro3) initiated by the International GNSS Service (IGS), 11 analysis centers (ACs) reanalyzed GPS/GLONASS/Galileo observations spanning 1994–2020 for station coordinates, satellite orbits, clocks, biases and attitudes. To improve the robustness of satellite products, the IGS AC Coordinator (ACC) carried out the satellite orbit combination, and the reference satellite attitudes were computed by the Technical University of Graz (TUG). The clock/bias combination was performed by Wuhan University via the IGS “Precise Point Positioning with Ambiguity Resolution” (PPP-AR) Pilot Project using the PRIDE <i>ckcom</i> software. This article aims at reporting the clock/bias combination results in the repro3. In particular, the consistencies for the combined GPS P1–P2/Galileo C1–C5 differential code biases (DCBs) and the GPS/Galileo uncalibrated phase delays (UPDs) among contributing ACs are all better than 0.1&nbsp;ns and 0.05 cycles, respectively. As a result, the consistencies for the combined GPS/Galileo satellite clocks/biases are better than 10&nbsp;ps, equating about 3&nbsp;mm which is very close to the nominal precision of carrier-phase. In general, the Hadamard deviation and PPP-AR results confirm the higher robustness of the combined satellite clock/bias products over their original AC-specific counterparts. This is because the combined satellite clock/bias products harvest the merits of AC-specific contributions by identifying and excluding outlier solutions from the combination process.</div> <b>Citation:</b> Geng, J., Yan, Z., Wen, Q. et al. Integrated satellite clock and code/phase bias combination in the third IGS reprocessing campaign. <i>GPS Solut </i>28, 150 (2024). https://doi.org/10.1007/s10291-024-01693-9

<div>Geoscience Australia currently retains the role of the International GNSS Service Analysis Centre Coordinator (IGS ACC) in collaboration with Massachusetts University of Technology (MIT). The IGS ACC is responsible for monitoring the quality of products submitted by individual analysis centers, and combining them to produce the official IGS products. The IGS ACC also has the overall responsibility for coordinating the changes, developments and improvements within the contributing analysis centers to produce the IGS products using the latest models and standards. This report details the IGS ACC activities over 2023, which included general quality assessment of the IGS combined products over 2023, introduction of a new IGS Analysis Center (JGX, Japan), extension of the combined products for the third IGS reprocessing campaign (repro3) for 2021-2022, and multi-GNSS ultra-rapid demonstration combined orbits.</div> <b>Citation for full report:</b> Dach, R., Bockmann, E. (eds.) (2024). International GNSS Service Technical Report 2023 (IGS Annual Report). IGS Central Bureau and University of Bern; Bern Open Publishing DOI 10.48350/191991

<div>Within the preparation for the release of the International Terrestrial Reference Frame 2020, the International GNSS Service (IGS) analysis centers (ACs) issued the results of the third reprocessing campaign (IGS Repro 3) of all the GNSS network solutions backwards starting from 1994. For the first time, the IGS reprocessing products include not just GPS and GLONASS, but also the Galileo constellation. In this study, we show the methodology and results of the orbit combination provided by the IGS Analysis Center Coordinator (IGS ACC) at Geoscience Australia. The quality of the provided combined orbit products was cross-checked with the individual IGS Repro3 AC contributions. The internal consistency of the individual AC solutions with the combined orbits was assessed based on the root mean square of the 3D orbit differences. In 2020, the mean consistency of the combination is at the level of 9, 23, and 15 mm for GPS, GLONASS, and Galileo, respectively. The external validation was performed using Satellite Laser Ranging (SLR) observations. We proposed a novel approach to handling detector-specific biases in the results of SLR validation, reducing the standard deviation of SLR residuals by up to 15% for Galileo FOC satellites. The method is based on bias referencing to single-photon SLR stations that are not affected by the retroreflector signature effect. The proposed approach increased the internal consistency of the SLR dataset, facilitating the detection of orbit modeling issues. The standard deviation of SLR residuals of the best individual solution versus the combined equals 13/14, 15/16, 17/16, 16/16 mm for Galileo-FOC, -IOV, GLONASS-K1B, -M, respectively. Therefore, the combined solution can be considered equal or slightly better in quality compared to the best individual AC solutions. Searching for patterns in SLR residuals for different satellite-Sun-Earth geometries reveals that some issues in orbit modeling are not fully diminished for individual ACs. Eventually, we proved that the delivered combined orbit product may be considered the best solution overall. The combined solution benefits from the best individual solutions for each satellite type.</div> <b> Citation:</b> Zajdel, R., Masoumi, S., Sośnica, K. et al. Combination and SLR validation of IGS Repro3 orbits for ITRF2020. J Geod 97, 87 (2023). https://doi.org/10.1007/s00190-023-01777-3

<div>Geoscience Australia currently performs the role of the International GNSS Service Analysis Centre Coordinator (IGS ACC) in a collaboration with Massachusetts University of Technology (MIT). The IGS ACC is responsible for monitoring the quality of products submitted by individual analysis centers, and combining them to produce the official IGS products. The IGS ACC also has the overall responsibility for coordinating the changes, developments and improvements within the contributing analysis centers to produce the IGS products using the latest models and standards. This report details the IGS ACC activities over 2022, which included the transition to a new reference frame IGS20 and results of the multi-GNSS combined orbit and clock products for Repro3.</div> <b>Citation:</b> Dach, R., Bockmann, E. (eds.) (2023). <i>International GNSSServiceTechnical Report 2022 (IGSAnnual Report)</i>. IGSCentral Bureau andUniversity of Bern; BernOpenPublishing DOI10.48350/179297

<div>FrontierSI has been engaged by Geoscience Australia (GA) to establish a series of case studies showcasing the benefits of Positioning Australia products and services through demonstrations of precise positioning capability. This case study is the second in the series and in a collaboration with The Bureau of Meteorology (BOM) it aims to explore the use of Ginan’s post-processing capabilities for determining receiver altitude and atmospheric parameters from global navigation satellite systems (GNSS) observations collected from a high-altitude balloon.</div>

<div>FrontierSI has been engaged by Geoscience Australia (GA) to establish a series of case studies showcasing the benefits of Positioning Australia products and services through demonstrations of precise positioning capability. This case study is the third in the series and in a collaboration with The Commonwealth Scientific and Industrial Research Organisation&nbsp;(CSIRO) it aims to explore the use of Ginan’s real-time and post-processing capabilities for determining water level height from a global navigation satellite systems (GNSS) receiver deployed on a floating pontoon on Googong Dam.</div>

<div>Ginan is a GNSS (Global Navigation Satellite System) analysis centre software that is currently being developed by Geoscience Australia in partnership with industry and academic partners. Ginan is fully open-source software based on the SSR (State Space Representation), PPP (Precise Point Positioning) model and is capable of computing precise positioning products, delivering real-time correction services, as well as operating as a user-driven precise positioning engine.</div><div><br></div><div>Ginan is a modern, multi-threaded C++ application that utilises industry standard high-performance libraries such as Eigen3, and Boost. Software configuration is managed through industry standard YAML (YAML Ain’t Markup Language) files. Standard IGS (International GNSS Service) file-based products are produced, and intermediate positioning products are managed in the open-source NoSQL MongoDB database and output is through standard Radio Technical Commission for Maritime Services-3 (RTCM3), IGS-SSR and Compact SSR message streams. At its core, Ginan is a customised and optimised Kalman filter that is tightly coupled with a data pre-processor and orbit integrator, enabling both real-time processing of industry standard RTCM3 data messages streams and post-processing using IGS positioning products.</div><div><br></div><div>The purpose of Ginan is to provide users with a unique multi-GNSS real-time processing platform capable of delivering precise positioning products to the Australian and international Positioning Navigation and Timing (PNT) community; support expert advice on navigation system performance over Australia; and provide state-of-the-art GNSS analysis centre software to universities and research organisations to enable Australia to lead in the development of geospatial technology. Ginan can be used for many geodetic and positioning activities such as computation of daily coordinate solutions, precise satellite orbit determination, computation of satellite clocks & biases, atmospheric modelling, data QA/QC and more. This paper describes the Kalman filter optimization methodology implemented in Ginan and provides benchmarking comparisons of Ginan against the International GNSS Service combined orbit and clock products. Abstract presented at the 2024 Institute of Navigation (ION) Pacific Positioning, Navigation and Timing (PNT) Conference Honolulu, Hawaii