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Improved High Precision GNSS Positioning with New Satellites and Signals Nick Talbot Research Fellow, Trimble Navigation Australia 2013 Surveying Expo.

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Presentation on theme: "Improved High Precision GNSS Positioning with New Satellites and Signals Nick Talbot Research Fellow, Trimble Navigation Australia 2013 Surveying Expo."— Presentation transcript:

1 Improved High Precision GNSS Positioning with New Satellites and Signals Nick Talbot Research Fellow, Trimble Navigation Australia 2013 Surveying Expo The Institution of Surveyors, Victoria

2 Overview  Introduction  GNSS Constellation Status  BeiDou System  CMRx Format  RTK Test Campaign  Test Results  Summary

3 Introduction  Currently 75 GNSS satellites in space  Expect to have 90 GNSS satellites in space by 2015; 120 satellites by 2020  45+ GNSS satellites in view over Asia / Pacific simultaneously by 2020  All GNSS satellites are capable of supporting metre-level and high-precision positioning at centimetre-level  Following presentation describes some of the challenges presented by new satellites and signals  Test results provided to illustrate the benefit of new satellites and signals with latest RTK hardware / firmware

4 GNSS Constellation Status SystemOriginCurrentFuture GPSUSA31 satellites; 20 IIA + IIR satellites with L1C/A, L2 PY 7 IIR-M satellites with L1C/A, L2C 4 IIF satellites with L1C/A, L2C, L5 3-Freq. fully available ~ 2018 GPS III ~ 2022 GLONASSRussia24 satellites; FDMA L1, L2 CDMA signals added in new K- series sats (L1, L2, L5); Planned compatibility with GPS, Galileo QZSSJapan1 satellite; Modernized GPS L1, L2, L5 + LEX signal Planned launch of 3 additional satellites by 2017 (1 GEO) GalileoEU4 operational satellites with E1, E5A, E5B, E6 (E1 compatible with GPS L1C) Full constellation (30 sats) ~ 2020 BeiDouChina14 satellites; 5 GEO; 6 MEO; 3 Inclined GEO with B1, B2, B3 Full constellation (35 sats – 5 GEO; 30 MEO) ~ 2020

5 L5 L2 LEX L1 L5 L2 L1 G2 G3 G1 E1 E5 E6 B1 B3 B2 RTX / OmniSTAR Frequency [MHz] GPS (US) Galileo (Europe) GLONASS (Russia) InmarSAT QZSS (Japan) IRNSS (India) BeiDou (China) SBAS (US) GNSS Spectrum  GNSS antennas and receiver RF components expanded to capture usable signals from E5 to G1 spectrum  Good compatibility between GPS, QZSS and SBAS signal structure  Long term compatibility on L1C and E1 signals with frequency and coding  Galileo-E6; BeiDou-B3; and QZSS-LEX bands are to be regulated (limited access), even though B3 can be tracked and used today for RTK

6 BeiDou System  Three satellite systems –BeiDou-1 (active ranging system) no Trimble support –BeiDou-2 (current system) used to be called Compass – subject of this talk –BeiDou-3 (proposal to move B1 to L1) first MEO satellites may launch in 2014  Current constellation –5 GEOs / 5 Inclined GEOs / 4 MEOs / More MEOs in 2014 –GEOs are harder to acquire & track due to high data rate (2ms versus 20ms pre detection interval) –Multipath errors are constant for static users of GEOs

7 BeiDou System  Signals –B1, B2 – supported by Maxwell VI ASIC  What’s public –B1 Open Service is “fully” public –B2 is an Open Service – not in the current ICD –B2 is the same signal as B1 so it is supported –B3 is officially a restricted signal – even though current codes appear to follow a defined polynomial

8 BeiDou Broadcast Orbit Daily Perf ormance – Based on RTX tracking network BeiDou dual-frequency code residuals, 7 May, 2013 RTX Station RMS [m]

9 CMRx Data Format GNSS corrections need to be transmitted to rover from a reference station or VRS network Additional satellite observations naturally increases the size of the GNSS correction stream Many radio solutions have limited bandwidth CMRx format provides a high level of data compression, with strong resistance to transmission errors

10 CMRx Data Format vs RTCM 3.x RTCM 3.1 GPS (L1, L2) + GLONASS (L1, L2) 9600 baud with 1 repeater (426 bytes/s)

11 CMRx Data Format vs RTCM 3.x CMRx GPS (L1, L2, L5) + GLONASS (L1, L2) + BeiDou (B1, B2) 9600 baud with 1 repeater (426 bytes/s) GLONASS + BeiDou 4 / 4 8 / 8 12 / 12

12 RTK Test Campaign  A test campaign was run in several regions around the world where GPS, GLONASS, BeiDou, QZSS and Galileo satellites are currently visible, including China, Australia and New Zealand  Data collected on baselines from 2km – 22km in a variety of environments:  Most in high multipath, trees, significantly masked environments  Some in relatively benign environments  15 different baselines  Most data collected in China  22km line from Perth Australia  6km line from Christchurch New Zealand

13 RTK Test Campaign  Tests conducted with Trimble R10; NetR9 receiver + Zephyr Geodetic 2 antenna, hardware  Real-time system testing performed in the field  PC version of RTK processor used to process logged GNSS data and analyze performance with various satellite systems enabled / disabled  Truth computed using post-processed RTX

14 Collective Results – Vertical 95% Christchurch, New Zealand

15 Collective Results – Horizontal 95%

16 RTK Example – Moderate Environment (Xi’an)  Data collected using R10 GNSS receiver in China –Supports GPS/GLONASS/Galileo/QZSS/BeiDou  Processed using a PC build of the real-time RTK engine –Operates in the same mode as real-time, no backward processing –Radio latency modeled –Operating mode set to kinematic –Data reprocessed with/without BeiDou  Environment was moderately difficult  Baseline length approximately 5km –Data collected in Xi’an

17 R10 GNSS Base Receiver Moderate Environment (Xi’an) – Base Station (not a recommended setup)

18 R10 GNSS Rover Receiver Moderate Environment (Xi’an) – Rover

19 Moderate Environment (Xi’an) – Satellite Tracking

20 Moderate Environment (Xi’an) – PDOP

21 Moderate Environment (Xi’an) – Height Error

22 Moderate Environment (Xi’an) – Horizontal Position Error

23 Galileo RTK Galileo satellites are currently unhealthy Trimble firmware is Galileo capable/ready. Modify firmware to force the satellites to report they are healthy and hence are used in the RTK solution Evaluate the RTK performance –2-hour period with 3 Galileo satellites. –2 identical rovers on an 8.9km line – real time test Common antenna Located in Melbourne Australia RX1 = GPS+GLN+QZSS+BDS+Galileo RX2 = GPS+GLN+QZSS+BDS

24 Number of satellites in RTK

25 Height Error

26 Summary  Current BeiDou constellation nearly doubles the number of visible satellites over Asia  Additional satellites improve accuracy of position estimates  Tests show addition of BeiDou improved 95% position errors by: –5-75% horizontal –8-68% vertical  Additional satellites help to reduce the overall impact of measurement noise and multipath errors

27 Summary  Similar incremental improvements in position accuracy noted with Galileo satellites in RTK solution  Additional satellites lead to increases in RTK correction bandwidth  CMRx format designed for increased satellite counts  CMRx roughly 55% smaller than RTCM v3.x  Expect to see significant improvements in position availability and accuracy when BeiDou, QZSS, Galileo constellations fully populated

28 Questions? Acknowledgements: Stuart Riley and Sunnyvale Team Eric Leroy (QA) App Firmware Team HCC/Survey/Infra/InTech H/W Team Timo Allison, Markus Glocker (Terrasat) TNZ & Westminster field testing Xi’an China team Dave Vanden Berg & InTech Beijing


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