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

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
System
Origin
Current
Future
GPS
USA
31 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
GLONASS
Russia
24 satellites; FDMA L1, L2
CDMA signals added in new K-series sats (L1, L2, L5); Planned compatibility with GPS, Galileo
QZSS
Japan
1 satellite;
Modernized GPS L1, L2, L5 + LEX signal
Planned launch of 3 additional satellites by 2017 (1 GEO)
Galileo EU
4 operational satellites with E1, E5A, E5B, E6 (E1 compatible with GPS L1C)
Full constellation (30 sats) ~ 2020
BeiDou
China
14 satellites; 5 GEO; 6 MEO; 3 Inclined GEO with B1, B2, B3
Full constellation (35 sats – 5 GEO; 30 MEO) ~ 2020

5. GNSS Spectrum L5 L2
LEX L1 G2 G3 G1 E1 E5 E6 B1 B3 B2
RTX / OmniSTAR
1164
1189
1214
1217
1237
1257
1260
1300
1525
1551
1559
1565
1571
1579
1585
1590
1599
1614
Frequency [MHz]
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
GPS (US)
Galileo (Europe)
GLONASS (Russia)
InmarSAT
QZSS (Japan)
IRNSS (India)
BeiDou (China)
SBAS (US)

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 Performance – Based on RTX tracking network
BeiDou dual-frequency code residuals, 7 May, 2013
RMS [m]
RTX Station

9. CMRx Data Format
Additional satellite observations naturally increases the size of the GNSS correction stream
GNSS corrections need to be transmitted to rover from a reference station or VRS network
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)
12 / 12
GLONASS + BeiDou
8 / 8
4 / 4

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

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

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