GPS Omnidirection Antenna Modem Beamed Development Update Antenna Base Base Station Urban Station Ring Navigation and positioning in China Urban Ring Line Users Line JiNgNaN LiU, ChUaNg shi, LiNyUaN Xia, aND hUi LiU FIGURE 1 Shenzhen CORS station established in China Base Station Urban Users Ring at applications for surveying and map- Base Station Urban Line Ring ping, urban planning, resource manage- Line ment, transportation monitoring, disas- ter prevention, and scientific research FM Station Base including meteorology and ionosphere Monitoring Burg Station scintillation. Positioning Center Enter into der Municipal Urban Signal mobile van In this way, the Shenzhen CORS net- Communication Ring Transmitter system work is acting to energize the booming Center Line economy of this young city. With rapid FIGURE 2 Lay out of CORS network in Shenzhen development of CORS construction in China, these stations are expected to operate within a standard national and SLR and pro- istockphoto.com/Hester GNSS RINEX Single Cleaned GNSS GNSS/LEO Satellite ICs © specification and to play vital roles in duce long baseline data station data data orbit Satellite cleaning SST ranging data integrator description During the past 15 years, China has steadily accelerated its activities in realization of the “digital city” in terms and satellite orbit SLR data Observed attitude of real-time and precise positioning and outputs. PANDA GNSS/LEO orbit Observed the realm of satellite navigation and positioning. Researchers from leading navigation. can perform orbit file acceleration GNSS engineering centers in Wuhan provide an overview of these efforts. Based on CORS stations properly determination for Data cleaning based Estimator Ambiguity on residuals/update • Least Square Adjustment contraints distributed throughout China, some of GPS and low earth initial values for high precision post- these facilities are aligned with stations orbiting (LEO) sat- mission applications Integer • Square Root Information evelopment of satellite-based southern California, USA. This innova- In contrast to preliminary stages, installed with other spatial observing ellites, and its results ambiguity Filter for kinematic or real- resolution positioning and naviga- tion successfully helped geologists to evolution of networks and communi- technologies such as SLR, VLBI and can match those of time applications tion technology has greatly deepen their understanding of seismic cations have enabled CORS to become DORIS (Doppler Orbitography and such agencies as the Post-fit residuals Dreformed conventional spatial faults because more continuous spatial a leading support component for the Radio-positioning Integrated by Satel- International GNSS Free/Fixed solutions determination practices and enabled information can be obtained than ever national temporal and spatial informa- lite, a system maintained by France). Service (IGS), JPL, Products Solution Combination Real-time Products advancement of the digital infrastruc- before. tion infrastructure. CORS is now imple- These sites are serving for satellite orbit Scripps Institution • Site deformation Products Generation • Site pos/vel. and • LEO orbit/trajectory Products Publication clocks ture in China. This kind of progress is From 1997 to 2000, as a key state sci- mented at many of China’s main cities, determination and, when combined with of Oceanography, • GNSS orbits and clocks • Zenith Troposphere continuing with the improvement of entific project, the Crust Motion Obser- such as Shenzhen, Chengdu, Beijing, multiple spatial technologies, have cre- the European Space • Earth rotation Delay parameters • LEO orbit/trajectory related techniques. vation Network of China (CMONOC) Shanghai, and Guangzhou. ated a dynamic and multi-dimensional Agency (ESA), the • Gravity model • GNSS orbits and This article will provide an update was implemented, composed of 25 CORS Among these, the Shenzhen CORS terrestrial reference frame for China. U.S. National Geo- • etc. clocks on China’s GNSS-related activities in stations and 1,000 regional network sta- system was started in 1999 as a paradigm detic Survey, the recent years, including research on novel tions. Very long baseline interferometry of comprehensive service network and PANDA & Orbit Center for Orbit FIGURE 3 Schematic design of PANDA software for satellite orbit determi- nation positioning approaches, collaborations (VLBI) and satellite laser ranging (SLR) spatial data infrastructure in China. (See Determination Determination in between China and international sec- equipment was coupled in some of the Figures 1 and 2.) The system was designed With funding support from relevant Europe (COD), tors, and, finally, some brief comments CORS stations. Based on CMONOC, and implemented in a flexible form of authorities, Wuhan University has Germany’s GeoForschung Zentrum Experiment-A (GRACE-A) satellite with on the prospect for China’s Beidou navi- researchers achieved significant seismic network and wireless communication developed a scientific software called (GFZ), and Canada’s Energy, Mines the satellite elevations computed by SLR gation and positioning system. motion results about continental plates. to perform a variety of positioning and PANDA (for Position and Navigation and Resources (now Natural Resources stations. CORS has subsequently been employed navigation services in both real-time Data Analysis) that comprehensively Canada) facility (EMR). In the software packages, we have China’s CORS Network by numerous agencies and organizations and postprocessing. analyzes multiple spatial observations Figure 4 compares the IGS and considered all possible parameters such Beginning in 1990, the mode of continu- in China and has become popular in The project was jointly accomplished and autonomously determines satellite PANDA orbit determination root mean as earth orientation and right-hand ously operating reference station (CORS) many fields, including guidance of air- by the GNSS Engineering Research Cen- orbits. Figure 3 shows the data process- square (RMS) fits of GPS orbits with the circular (RHC) phase-rotation correc- using GPS was first applied by NASA’s craft similar to the U.S. Wide Area Aug- ter, Wuhan University, and Shenzhen ing scheme of the PANDA software. results from IGS Analysis Centers. Fig- tions, and various force models includ- Jet Propulsion Laboratory (JPL) and mentation System (WAAS) approach Municipal Bureau of Land Resources The software can currently accom- ure 5 compares PANDA range residuals ing gravity model, third-body attraction, MIT to the research of plate tectonics in procedures. and Housing Management. It is aimed modate observations including GPS to the Gravity Recovery And Climate tides, atmospheric drag, solar radiation, 46 InsideGNSS september 2006 www.insidegnss.com www.insidegnss.com september 2006 InsideGNSS 47 DevelopmeNt in china 90 0.100 60 single-frequency GPS receivers. Studies Recently, a study has 50 are focusing on compensation methods gotten under way on the 0.050 ACs ACs 40 for ionospheric delay, phase unwrap- potential use of combina- 60 (2004) 0.000 30 ping, and receiver bias–induced effects, tions of three or multiple which will lead to further refinements of frequencies and their prop- 20 Elevation (o) Residuals (m) -0.050 this positioning approach. erties in light of the Gali- 30 10 SLR residuals Elevation To meet user requirement for accu- leo system. Research is also -0.100 0 rate three-dimensional (3-D) position- being conducted on the Orbit RMS wrt IGS (mm) FIGURE 5 Residuals by PANDA and elevations of satellite laser ranging ing in local datums, research on refined realization and improve- 0 cod em gfz jpl sio es ng g+c (fix g+c (free) gps (fix) gps (free) observations to GRACE-A a s quasi-geoids is now fully performed ment of the Galileo Ter- r in most big cities in China. Tests have restrial Reference Frame ) kinematic applica- tion, GPS attitude control, and gravity shown that refined quasi-geoid results combining observations tions. model recovering. can achieve levels of geoid height results from Galileo, VLBI, SLR, FIGURE 4 Overall PANDA orbit RMS (in millimeters) compared with the Fig- IGS final results. Green is that of PANDA, yellow is for that of the IGS In the future, With precise orbit support and flexi- with centimeter-level accuracy. (See DORIS, and other sources. Analysis Centers (ACs) over the same time, and red for ACs around the signal observations ble services including atmospheric prod- ure 6.) This can further enable position- end of 2004. from Galileo and ucts by IGS and other agencies, single ing and navigation, including 3-D pre- the Beidou System other systems will point positioning is also rapidly push- cise point positioning relative to local China’s third Beidou velocity impulse, and acceleration obser- be included in the software to further ing towards maturity in China using height datums by using GNSS. navigation satellite was vations. Some ambiguous factors can be enrich its orbit determination capability. refined ambiguity resolution algorithms. launched into orbit on May compensated by estimated parameters. Some recently planned research aspects Research results by Wuhan University international Cooperation 25, 2003 (see Figure 7). That Observation equations are generated for this software may cover tropospheric and other departments show that the Apart from research based on current marked the formation of epoch by epoch within an estimator to delay estimation from a moving plat- accuracy