RTK from space: a novel and low-cost GNSS augmentation technique for LEO communication satellites

Low Earth Orbit (LEO) satellites are widely used in mobile communications. They can be used to provide navigation services by broadcasting navigation signals and augmentation information. However, it is extremely expensive to construct a mega constellation of LEO satellites equipped with navigation payloads. A better way would be making good use of the LEO communication satellites equipped with high-precision GNSS receivers. In this paper, we proposed a novel and low-cost Global Navigation Satellite System (GNSS) augmentation technique named “Real Time Kinematic (RTK) from space” for the LEO communication satellites. In the proposed algorithm, LEO satellites provide spatial datum for positioning users with their precise orbits. Through the communication link, users can obtain real-time augmentation information, including GNSS precise ephemeris, the onboard GNSS observations, centre of mass of LEO satellites, and the LEO satellites attitude quaternions. Using the augmentation information, user terminals can achieve precise positioning with fast ambiguity fixing. To validate the algorithm, we conduct experiments using simulated data and real-world data. The simulation experiments indicate that the GPS only solution needs around 35 seconds to get ambiguity fixed while GPS and BeiDou dual sytems take 37.1% less time. In terms of positioning accuracy, the GPS only solution has an 3D RMS (Root Mean Squared) of 1.93 cm while 1.48 cm for GPS + BDS. Real-world data experiments using GRACE-FO-C satellite and four IGS stations (ABMF, ABPO, AGGO and WUH2) show an average fixing time of 22.7 epochs. The average positioning errors in the east, north, and up directions are 2.4 cm, 2.6 cm, and 5.3 cm, respectively.