Workshop 2018
Bryan Stressler - An Assessment of the Accuracy of Broadcast Ephemerides for Multi-GNSS Positioning - October 29, 2018 • 106 Views
Accurately determined satellite coordinates are a crucial component for achieving high-accuracy results in GNSS positioning. IGS provides GNSS orbits that are available with latencies varying from real time for broadcast and predicted ultra-rapid ephemerides to approximately two weeks for final IGS orbits. Depending on the application, real time or low latency (ultra-rapid or rapid) IGS orbit products may be required at the cost of lower positional accuracy. The availability of new GNSS constellations such as Galileo and BeiDou, along with updates to the legacy GPS and GLONASS constellations, present great potential for improved positioning solutions, but also pose new challenges in utilizing new observables and modeling satellite orbits. In addition to exploring the characteristics of the new observables, it is important to evaluate the quality of satellite ephemerides to identify potential limitations and thus improve multi-GNSS processing strategies. Here we evaluate the accuracy of broadcast orbits for each of the four global constellations (GPS, GLONASS, Galileo and BeiDou) provided in daily broadcast navigation files. For each set of broadcast elements, we compute the satellite coordinates and compare the results to the corresponding interpolated coordinates from a sp3 final orbit file. Corrections are applied to ensure that each position is appropriately referenced to the satellite antenna phase center. Our comparison shows that the broadcast ephemerides for GPS and Galileo typically agree at meter to sub-meter levels, while GLONASS and BeiDou orbits agree within several meters and up to greater than 10 meters at times.

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