By adopting the real-time observations of IGS, multi-GNSS experiment (MGEX) and national BDS augmentation service system (NBASS), BDS real-time wide-area precise positioning service system is developed, which can generate high accuracy BDS real-time orbits, clocks and ionosphere products and provide centimeter-, decimeter-and meter-level positioning service with different positioning modes including BDS dual-and single-frequency precise point positioning (PPP) and single point positioning (SPP). The evaluation results of real-time products show that the user range error (URE) of BDS real-time orbits and clocks is about 2.0 cm and the accuracy of real-time ionosphere products is better than 4.0 TECU. The performance of real-time kinematic positioning at the 95% confidence level is evaluated by real-time stations across China. It reveals that the BDS dual-frequency PPP shows significant regional characteristic, the accuracy in high-latitude and western fringe region is about 0.2 m and 0.3 m in the horizontal and vertical component, respectively, while the horizontal accuracy is better than 0.1 m and the vertical accuracy is better than 0.2 m in the midlands, which is close to the accuracy of GPS real-time PPP. By the combination of BDS and GPS, the BDS/GPS PPP can improve the positioning performance of GPS or BDS PPP, especially improves the PPP convergence time significantly and the convergence time is within 20 min. In addition, except the fringe region, BDS single-frequency PPP can achieve 0.5 m in horizontal component and 1.0 m in vertical component, BDS SPP can achieve 2.0 m and 3.0 m in horizontal and vertical components, respectively.
[1] 杨元喜. 北斗卫星导航系统的进展、贡献与挑战[J]. 测绘学报, 2010, 39(1):1-6. YANG Yuanxi. Progress, Contribution and Challenges of Compass/BeiDou Satellite Navigation System[J]. Acta Geodaetica et Cartographica Sinica, 2010, 39(1):1-6.
[2] YANG Yuanxi, LI Jinlong, XU Junyi, et al. Contribution of the Compass Satellite Navigation System to Global PNT Users[J]. Chinese Science Bulletin, 2011, 56(26):2813-2819.
[3] MONTENBRUCK O, HAUSCHILD A, STEIGENBERGER P, et al. Initial Assessment of the Compass/BeiDou-2 Regional Navigation Satellite System[J]. GPS Solutions, 2013, 17(2):211-222.
[4] SHI Chuang, ZAHO Qile, HU Zhigang, et al. Precise Relative Positioning Using Real Tracking Data from Compass GEO and IGSO Satellites[J]. GPS Solutions, 2013, 17(1):103-119.
[5] 杨元喜, 李金龙, 王爱兵, 等. 北斗区域卫星导航系统基本导航定位性能初步评估[J]. 中国科学:地球科学, 2014, 44(1):72-81. YANG Yuanxi, LI Jinlong, WANG Aibing, et al. Preliminary Assessment of the Navigation and Positioning Performance of BeiDou Regional Navigation Satellite System[J]. Science China:Earth Sciences, 2014, 57(1):144-152.
[6] HE Haibo, LI Jinlong, YANG Yuanxi, et al. Performance Assessment of Single-and Dual-frequency BeiDou/GPS Single-epoch Kinematic Positioning[J]. GPS Solutions, 2014, 18(3):393-403.
[7] GU Shengfeng, LOU Yidong, SHI Chuang, et al. BeiDou Phase Bias Estimation and Its Application in Precise Point Positioning with Triple-frequency Observable[J]. Journal of Geodesy, 2015, 89(10):979-992.
[8] 朱永兴, 冯来平, 贾小林, 等. 北斗区域导航系统的PPP精度分析[J]. 测绘学报, 2015, 44(4):377-383. DOI:10.11947/j.AGCS.2015.20140082. ZHU Yongxing, FENG Laiping, JIA Xiaolin, et al. The PPP Precision Analysis Based on BDS Regional Navigation System[J]. Acta Geodaetica et Cartographica Sinica, 2015, 44(4):377-383. DOI:10.11947/j.AGCS.2015.20140082.
[9] DOW J M, NEILAN R E, RIZOS C. The International GNSS Service in a Changing Landscape of Global Navigation Satellite Systems[J]. Journal of Geodesy, 2009, 83(3-4):191-198.
[10] MONTENBRUCK O, STEIGENBERGER P, KHACHIKYAN R, et al. IGS-MGEX:Preparing the Ground for Multi-constellation GNSS Science[J]. Inside GNSS, 2014, 9(1):42-49.
[11] DAI Xiaolei, GE Maorong, LOU Yidong, et al. Estimating the Yaw-attitude of BDS IGSO and MEO Satellites[J]. Journal of Geodesy, 2015, 89(10):1005-1018.
[12] ZHANG Weixing, LOU Yidong, GU Shengfeng, et al. Joint Estimation of GPS/BDS Real-time Clocks and Initial Results[J]. GPS Solutions, 2016, 20(4):665-676.
[13] LIU Jingnan, GE Maorong. PANDA Software and Its Preliminary Result of Positioning and Orbit Determination[J]. Wuhan University Journal of Natural Sciences, 2003, 8(2B):603-609.
[14] SHI Chuang, ZHAO Qile, GENG Jianghui, et al. Recent Development of PANDA Software in GNSS Data Processing[C]//Proceedings of the International Conference on Earth Observation Data Processing and Analysis. Wuhan, China:SPIE, 2008.
[15] GE Maorong, CHEN Junping, DOUŠA J, et al. A Computationally Efficient Approach for Estimating High-rate Satellite Clock Corrections in Realtime[J]. GPS Solutions, 2012, 16(1):9-17.
[16] KOUBA J. A Simplified Yaw-attitude Model for Eclipsing GPS Satellites[J]. GPS Solutions, 2009, 13(1):1-12.
[17] SHI Chuang, ZHENG Fu, LOU Yidong, et al. National BDS Augmentation Service System (NBASS) of China:Progress and Assessment[J]. Remote Sensing, 2017, 9(8):837.
[18] RODRIGUEZ-SOLANO C, HUGENTOBLER U, STEIGENBERGER P. Solar Radiation Pressure and Attitude Modeling of GNSS Satellites[C]//Proceedings of the American Geophysical Union Fall Meeting 2011. San Francisco:AGU, 2011.
[19] SCHMID R, STEIGENBERGER P, GENDT G, et al. Generation of a Consistent Absolute Phase-center Correction Model for GPS Receiver and Satellite Antennas[J]. Journal of Geodesy, 2007, 81(12):781-798.
[20] DILSSNER F, SPRINGER T, SCHÖNEMANN E, et al. Estimation of Satellite Antenna Phase Center Corrections for BeiDou[C]//Proceedings of the IGS Workshop 2014. Pasadena:IGS, 2014:23-27.
[21] WU J T, WU S C, HAJJ G A, et al. Effects of Antenna Orientation on GPS Carrier Phase[C]//Astrodynamics 1991:Proceedings of the AAS/AIAA Astrodynamics Conference. San Diego, CA:Univelt Inc., 1992:1647-1660.
[22] LOU Yidong, GONG Xiaopeng, GU Shengfeng, et al. Assessment of Code Bias Variations of BDS Triple-frequency Signals and Their Impacts on Ambiguity Resolution for Long Baselines[J]. GPS Solutions, 2017, 21(1):177-186.
[23] SAASTAMOINEN J. Atmospheric Correction for the Troposphere and Stratosphere in Radio Ranging Satellites[M]//HENRIKSEN S W, MANCINI A, CHOVITZ B H. The Use of Artificial Satellites for Geodesy. Washington DC:American Geophysical Union, 1972:247-251.
[24] LAGLER K, SCHINDELEGGER M, BÖHM J, et al. GPT2:Empirical Slant Delay Model for Radio Space Geodetic Techniques[J]. Geophysical Research Letters, 2013, 40(6):1069-1073.
[25] LOU Yidong, ZHANG Weixing, WANG C, et al. The Impact of Orbital Errors on the Estimation of Satellite Clock Errors and PPP[J]. Advances in Space Research, 2014, 54(8):1571-1580.
[26] SHI Chuang, GU Shengfeng, LOU Yidong, et al. An Improved Approach to Model Ionospheric Delays for Single-frequency Precise Point Positioning[J]. Advances in Space Research, 2012, 49(12):1698-1708.
[27] LOU Yidong, ZHENG Fu, GU Shengfeng, et al. Multi-GNSS Precise Point Positioning with Raw Single-frequency and Dual-frequency Measurement Models[J]. GPS Solutions, 2016, 20(4):849-862.
