<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>The Pacific Islands Applied Geoscience Commission (SOPAC) requested Geoscience Australia to compute International Terrestrial Reference Frame (ITRF) coordinates for 18 survey sites on islands in the northern Fiji archipelago from continuous geodetic GPS measurements observed from 8th July to 5th August 2008 inclusive. The GPS data was processed using version 5.0 of the Bernese GPS Software in a regional network together with selected IGS sites. The GPS solution was constrained to the ITRF2005 reference frame through adopting IGS05 coordinates on selected IGS reference sites and using the final IGS earth orientation parameters and satellite ephemerides products.</div><div>These coordinates provide the coordinate reference frame to be used to define Fiji’s claim to extended continental shelf under the provisions of Article 76 of the United Nations Convention on the Law of the Sea.</div><div><br></div>

<div>The annual Asia Pacific Regional Geodetic Project (APRGP) GPS campaign is an activity of the Geodetic Reference Frame Working Group (WG) of the Regional Committee of United Nations Global Geospatial Information Management for Asia and the Pacific (UN-GGIM-AP). This document describes the data analysis of the APRGP GPS campaign undertaken between the 10th and 17nd of September 2023. Campaign GPS data collected at 124 sites in nine countries across the Asia Pacific region were processed using version 5.2 of the Bernese GNSS Software in a regional network together with selected IGS (International GNSS Service) sites. The GPS solution was constrained to the ITRF2020 reference frame by adopting IGS20 coordinates on selected IGS core reference sites and using the final IGS earth orientation parameters and satellite ephemerides products. The average of the root mean square repeatability of the station coordinates for the campaign was 2.5 mm, 2.5 mm and 6.9 &nbsp;mm in north, east and up components of station position respectively.</div><div><br></div>

The annual Asia Pacific Regional Geodetic Project (APRGP) GPS campaign is an activity of the Geodetic Reference Frame Working Group (WG) of the Regional Committee of United Nations Global Geospatial Information Management for Asia and the Pacific (UN-GGIM-AP). This document describes the data analysis of the APRGP GPS campaign undertaken between the 15th and 22nd of September 2019. Campaign GPS data collected at 101 sites in ten countries across the Asia Pacific region were processed using version 5.2 of the Bernese GNSS Software in a regional network together with selected IGS (International GNSS Service) sites. The GPS solution was constrained to the ITRF2014 reference frame by adopting IGS14 coordinates on selected IGS reference sites and using the final IGS earth orientation parameters and satellite ephemerides products. The average of the root mean square repeatability of the station coordinates for the campaign was 1.8 mm, 1.6 mm and 5.4 mm in north, east and up components of station position respectively.