Abstract
The Chinese Area Positioning System (CAPS) is a new positioning system developed by the Chinese Academy of Sciences based on the communication satellites in geosynchronous orbit. The CAPS has been regarded as a pilot system to test the new technology for the design, construction and update of the BeiDou Navigation Satellite System (BDS). The system structure of CAPS, including the space, ground control station and user segments, is almost like the traditional Global Navigation Satellite Systems (GNSSs), but with the clock on the ground, the navigation signal in C waveband, and different principles of operation. The major difference is that the CAPS navigation signal is first generated at the ground control station, before being transmitted to the satellite in orbit and finally forwarded by the communication satellite transponder to the user. This design moves the clock from the satellite in orbit to the ground. The clock error can therefore be easily controlled and mitigated to improve the positioning accuracy. This paper will present the performance of CAPS-based relative positioning and velocity estimation as assessed in Beijing, China. The numerical results show that, (1) the accuracies of relative positioning, using only code measurements, are 1.25 and 1.8 m in the horizontal and vertical components, respectively; (2) meanwhile, they are about 2.83 and 3.15 cm in static mode and 6.31 and 10.78 cm in kinematic mode, respectively, when using the carrier-phase measurements with ambiguities fixed; and (3) the accuracy of the velocity estimation is about 0.04 and 0.11 m/s in static and kinematic modes, respectively. These results indicate the potential application of CAPS for high-precision positioning and velocity estimation and the availability of a new navigation mode based on communication satellites.
Highlights
With the highly accurate performance of Positioning, Navigation and Timing (PNT), GlobalNavigation Satellite Systems (GNSSs), being of all-weather and real-time operational PNT service over land, sea, and even aerospace, have been developed rapidly around the globe [1]
The performance of Standard Point Positioning (SPP) based on Chinese Area Positioning System (CAPS) was assessed by the simulated and real data in the previous studies [5,10] and the results showed that CAPS can independently achieve the SPP with an accuracy of 10 to 20 m, which was comparable to the SPP performance of traditional Global Navigation Satellite Systems (GNSSs)
The antenna in our experiment was installed on the roof of the Academy of Opto-Electronics (AOE) in Beijing, China, and the CAPS navigation signals from the 4 GEO satellites and 1 IGSO satellite were tracked by our receivers during the experiment period
Summary
With the highly accurate performance of Positioning, Navigation and Timing (PNT), Global. There are some challenges that have to be faced by the growing development of GNSS systems [3], i.e., (1) service capabilities through positioning, velocity estimation and time service without communication, (2) the weakness of the received signal, with fixed satellites/frequencies/code making the signal vulnerable to interference, and (3) the PNT accuracy of current GNSSs is significantly dependent on the performance of satellite clock which is extremely difficult to be kept stable in orbit [4]. The conclusion and future work are drawn out in the final section
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