This paper proposes new sets of suitable broadcast ephemeris parameters for geosynchronous (GEO) and inclined geosynchronous (IGSO) navigation satellites (NSs). Despite the increasing number of GEO and IGSO NSs, global positioning system (GPS)-type ephemeris parameters are still widely used for them. In an effort to provide higher fit accuracy, we analyze a variety of broadcast ephemeris parameters for GEO and IGSO satellites along with their orbital characteristics and propose optimal sets of parameters. Nonsingular elements and orbital plane rotation are adopted for alleviating/avoiding the singularity issues of GEO satellites. On the basis of 16 parameters of GPS LNAV, we add one to four parameters out of 28 correction ones to determine optimal sets of ephemeris parameters providing higher accuracy. All possible parameter sets are tested with the least-square curve fit for four BeiDou GEOs and six BeiDou IGSOs. Their fit accuracies are compared to determine the optimal broadcast ephemeris parameters that provide minimum fit errors. The set of optimal ephemeris parameters depends on the type of orbit. User range error (URE) accuracies of the proposed optimal ephemeris parameters ensure results within 2.4 cm for IGSO and 3.8 cm for GEO NSs. Moreover, the experimental results present common parameter sets for both IGSO and GEO for compatibility and uniformity. Compared with four conventional/well-known sets of ephemeris parameters for BeiDou, our proposed parameters can enhance accuracies of up to 34.5% in terms of URE. We also apply the proposed optimal parameter sets to one GEO and three IGSO satellites of QZSS. The effects of fitting intervals, number of parameters, total bits, and orbit types on the fit accuracy are addressed in detail.

This study proposes real-time orbit/clock determination of Korean Navigation Satellite System (KNSS), which employs the kinematic precise point positioning (PPP) solutions of multiple Global Navigation Satellite System (multi-GNSS) to compensate for receiver clock offset. Global visibility of KNSS satellites in terms of geometric coverage is first analyzed for the purpose of selecting optimal locations of KNSS monitoring stations among International GNSS Service (IGS) and Multi-GNSS Experiment (MGEX) network. While the receiver clock offset is obtained from multi-GNSS PPP clock solutions of real observation data, KNSS measurements are simulated from the dynamically propagated KNSS reference orbit and the receiver clock offset. The offset and drift of satellite clock are also generated based on two-state clock model considering atomic clock noise. Real-time orbit determination results are compared with an artificially generated true or bit, wihch show 0.4m and 0.5m of 3-dimensional root-mean-square (RMS) position errors for geostationary (GEO) and ellitically-inclined-geosynchronous-orbit (EIGSO) satellites, respectively. The overall results show that the real-time precise orbit determination of KNSS should be achievable in meter level by installing KNSS-compatible multi-GNSS receivers on the IGS and/or MGEX network. The overall process can be also used to verify integrity of KNSS monitoring stations.