On May 27, 2021, the 12th China Satellite Navigation Conference S04 Session Satellite Orbits and Precise Positioning was successfully held in the Multi-function Hall 205-A on the second floor of Primus Hotel Nanchang International Expo City. The Session was chaired by Hu Xiaogong, Li Jianwen and Li Bofeng, Chairmen of the Session. The topics of the Session include: precise orbit determination and applications and precise positioning and applications. Many experts and scholars from the industry participated in the Session. Speakers actively shared their insights with the audience, which led to heated discussions.
The Session invited a total of 8 experts, including Tseng Tzupang from Geoscience Australia, Researcher Ruan Rengui from Xi'an Institute of Surveying and Mapping, Professor Zhao Qile from Wuhan University, Expert Tang Chengpan from Shanghai Astronomical Observatory of Chinese Academy of Sciences, Professor Xu Peiliang from Disaster Prevention Research Institute and Researcher Yuan Yunbin from Innovation Academy for Precision Measurement Science and Technology of Chinese Academy of Sciences to give their authoritative interpretations.
Prof. Tseng Tzupang of Geoscience Australia conducted research on the application of solar radiation pressure model in GNSS-based orbit determination and proposes a new solar radiation pressure model ECOMC. The ECOMC hybrid model can overcome the periodic errors caused by the interaction of SRP force and RTN coordinate system, and can effectively compensate for the deficiencies of ECOM1 and ECOM2. Compared with the IIF satellites supported by ECOM2 model correction, the orbit accuracy of IIF satellites supported by ECOMC model correction has increased by 13.2%, 14.8% and 42.6% in the RTN direction respectively and the orbit accuracy of IIR satellites can be increased by 7.4%, 7.7% and 35.0% in the RTN direction respectively using the ECOMC model for correction. The PPP results resolved by the ECOMC hybrid model can be improved by 20% and 13% compared with the PPP results resolved by the ECOM2 and ECOM1 models respectively.
Dr. Ruan Rengui collected statistics on the BDS-3 precise orbit products provided by different agencies and found that the consistency of different agencies' products was poor. Dr. Ruan also found that there were obvious systematic biases in SLR checks of orbit products from most analysis centers; ECOM1 and ECOM2 models did not show consistent advantages and disadvantages in the two indicators of orbit overlap segment and laser residual, and BW, ERP and AT showed no significant improvement for the indicator of orbit overlap segment; crosslink data combined with regional or global monitoring stations could significantly improve the orbit accuracy.
Prof. Zhao Qile constructed the geometric and dynamical models for high-precision spatio-temporal datum determination based on the important and difficult problems such as yaw attitude model, millimeter-level calibration of receiver and antenna phase center, solar radiation pressure model for crosslink ranging bias and thermal radiation force model. The models built by Prof. Zhao have already enabled the provision of high-precision spatio-temporal datum products and their integrated products with 1.0 mm horizontal accuracy and 3.4 mm elevation accuracy for the base stations at home and abroad and have ensured that the accuracy of spatial signals of orbits + clock errors can meet the positioning accuracy requirements of 5mm horizontal accuracy and 50px elevation accuracy. At the end of his presentation, Prof. Zhao proposed the ubiquitous mobile terminal to assist the augmentation of distributed navigation of refined atmospheric model, which could help fuse multi-source ubiquitous information for provision of high-precision location-based services.
Expert Tang Chengpan from Shanghai Astronomical Observatory of Chinese Academy of Sciences firstly proposed a self-consistent resolution method for orbits and clock errors based on multi-satellite orbit determination considering information on changes in satellite clock errors in response to the self-consistency issues related to BDS satellite orbits and clock errors encountered in BDS-2 construction. Mr. Tang also analyzed the improvement of BDS-3 spatial signal accuracy and proposed a data processing method that was significantly different from ODTS.
Researcher Zhang Baocheng summarized the characteristics of PPP-RTK and conducted experiments on real-time non-differential non-combined PPP-RTK and pointed out that the PPP-RTK reference station spacing is 100-200km, which is more advantageous in the processing of CORS network data in multi-frequency and multi-system scenarios in the future. Mr. Zhang indicated that the results of the simulated dynamic test showed that real-time non-differential non-combined PPP-RTK could achieve instantaneous convergence, millimeter-level horizontal accuracy and centimeter-level elevation accuracy, and the test results of the UAV and agricultural machine using the self-developed terminal showed that the positioning errors were better than 50px in horizontal positioning and 125px in elevation positioning, and the data availability rate was higher than 98%.
Professor Xu Peiliang from Disaster Prevention Research Institute of Kyoto University, Japan, explained the characteristics of short-term PPP and its difference from long-term PPP and successfully applied short-term PPP in seismic waveform measurement. Prof. Xu indicated that the experimental results showed that millimeter-level positioning accuracy of seismic waveforms could be obtained without a (fixed) reference point.
The 8 authoritative experts in the field of satellite orbits and precise positioning have many years of scientific research experience, reaped fruitful academic achievements and engineering practice results. The presentations given by these experts were in-depth and easy to understand, systematic and comprehensive, accompanied by lively exchanges and interactions onsite. The Session is a complete success.