Abstract
The Beidou navigation satellite system is a very important sensor for positioning in the Asia-Pacific region. The Beidou inclined geosynchronous orbit (IGSO) and medium Earth orbit (MEO) satellites have been analysed in some studies previously conducted by other researchers; this paper seeks to gain more insight regarding the geostationary earth orbit (GEO) satellites. Employing correlation analysis, Fourier transformation and wavelet decomposition, we validate whether there is a systematic bias in their multipath combinations. These biases can be observed clearly in satellites C01, C02 and C04 and have a great correlation with time series instead of elevation, being significantly different from those of the Beidou IGSO and MEO satellites. We propose a correction model to mitigate this bias based on its daily periodicity characteristic. After the model has been applied, the performance of the positioning estimations of the eight stations distributed in the Asia-Pacific region is evaluated and compared. The results show that residuals of multipath series behaves random noise; for the single point positioning (SPP) and precise point positioning (PPP) approaches, the positioning accuracy in the upward direction can be improved by 8 cm and 6 mm, respectively, and by 2 cm and 4 mm, respectively, for the horizontal component.
Highlights
The Beidou navigation system has been providing position, navigation and timing (PNT) services since 27 December 2012, focusing on the whole Asia-Pacific region
Most To of the stations come from the MGEX network, except whichhow comes from show the periodicity characteristic of the code bias, station as wellBJF1, as present to detect the network
The most recent GNSS observables collected from eight stations in the Asia-Pacific region are employed to investigate the characteristic of code bias of the Beidou geostationary earth orbit (GEO) satellites
Summary
The Beidou navigation system has been providing position, navigation and timing (PNT) services since 27 December 2012, focusing on the whole Asia-Pacific region. Several studies and experiments on Beidou have been conducted, on the precise applications [1,2,3,4,5]. Wuhan University can provide the daily Beidou precise ephemeris, determined using the BeiDou Experimental Tracking Stations [BETS] data, and the orbit precision of the IGSO and MEO satellites can reach 10 cm in the radial direction [4]. In the Asia-Pacific region, Beidou is considered as a relevant and valuable complement to legacy systems for establishing improved GNSS services in this area [2]. Using the PPP approach to determine zenith tropospheric delay (ZTD), the Sensors 2016, 16, 1252; doi:10.3390/s16081252 www.mdpi.com/journal/sensors
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