Combination of GNSS orbits using least-squares variance component estimation

Abstract Over the past years, International GNSS Service (IGS) has been putting efforts into extending its service by setting up and running Multi-GNSS experiment pilot project (MGEX). Several MGEX analysis centers (ACs) contribute providing solutions containing not only GPS GLONASS but also Galileo, BeiDou, QZSS. As current IGS combination software can handle orbits of one constellation at a time, it requires substantial modifications to obtain consistent orbit product. In this contribution, we present least-squares framework for combination, where weights used combine ACs’ are determined variance component estimation. We introduce compare two weighting strategies, either AC-specific or AC constellation-specific used. An automated Z-score test is implemented yielding common set core satellites that determine weights. Both strategies tested using period half years. They yield similar results with an agreement centimeter level few centimeters other constellations. The 3D-RMS generally slightly better weighting. A comparison our approach official three years shows than 5 mm 12 GLONASS, respectively, while around $$15\,\textrm{mm}$$ 15 mm . external validation satellite laser ranging mean residuals combined products $$-3\,\textrm{mm}$$ - 3 $$6\,\textrm{mm}$$ 6 $$-8\,\textrm{mm}$$ 8 $$-31\,\textrm{mm}$$ 31