First Experiences of using BeiDou in a multi-

system GNSS receiver for precision

applications

Stuart Riley (Stuart_Riley@Trimble.com)

Trimble, USA

Introduction

BeiDou / Galileo Overview and Products

Observable Performance

BeiDou Autonomous Position Performance

Dynamic Testing

RTK Performance – Compromised Environment

RTK Performance – Benign Environment

Five system RTK

– GPS+GLN+QZSS+BDS+Galileo

Multiple Baseline BDS RTK performance

Conclusion

Example BeiDou Products

Also support GPS, GLONASS, Galileo, QZSS, SBAS (WAAS, EGNOS, MSAS etc)

OmniSTAR / RTX optionally available on some products

Chennai - BeiDou PRN 2 (GEO)

MP-B1 1-Sigma = 29cm

No code/carrier smoothing

Long Period/Diurnal Mulitpath Present

Chennai - Galileo Code Multipath

Beijing Data – relative to RTX truth

3D Position Error

BDS Clock analysis from 2011

Shinjuku Area – Tokyo Nov. 2011

GPS+GLONASS+IMU Post Process

GPS+GLONASS+QZSS

GPS+GLONASS+QZSS+BeiDou Reprocessed now the ICD is available

RTK Example – Moderate Environment

Data collected using R10 GNSS receivers by Trimble Xi’an Team

– Supports GPS/GLONASS/Galileo/QZSS/BeiDou

Processed using a PC build of the real-time RTK engine

– Operates in the same mode as realtime, no backward processing

– Radio latency modelled

– Operating mode set to kinematic

– Data reprocessed with/without BeiDou

Environment was moderately difficult

Baseline length approximately 5km

– Data collected in Xi’an

Truth computed by post-processed RTX

Base Station

Rover

Xi’an RTK Height Error

Xi’an RTK East/North Error

Xi’an RTK Initialization Time

Total Number Inits = 173

GPS+GLN+QZSS

Mean Init Time = 10 Sec

Max Init Time = 147 Sec

GPS+GLN+QZSS+BDS

Mean Init Time = 2 Sec

Max Init Time = 18 sec

Xi’an Number of satellites used

RTK Example – Benign Environment

8.9km Baseline Length

– Base on the roof of a house

– Rover on the roof of an office

Melbourne Australia (38o South / 145o East)

Melbourne East/North Error

Melbourne – Benign Environment

East/North 8.9mm versus 9.4mm (5% improvement)

Negligible change in the height 1-sigma

Average number of satellites in the RTK solution 23.4 versus 15.7

With BDS 19-29 SVs

W/o BDS 13-20 SVs

Mean PDOP 1.17 versus 1.37

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

Web GUI position page example

Number of satellites in RTK

Height Error

RTK Analysis

• Collect data on baselines from 2km – 22km

• Data from a variety of environments

• Some in relatively benign environments

• Most in high multipath, trees, significantly masked environments

• 15 different baselines

• Most data in China

• 22km line from Perth Australia

• 6km line from Christchurch New Zealand

• Processed in two modes

• GPS+GLN+QZSS

• GPS+GLN+QZSS+BDS

• Use a PC build of the code embedded in the receiver

• Processed in kinematic mode

Vertical 95%

Christchurch,

New Zealand

Horizontal 95%

Conclusions Trimble is rolling out BeiDou updates to a

variety of products

BeiDou produces high quality observables

Customers increasingly use GNSS for

PVT in harsh environments

– BeiDou in the greater Asia region provides

improvement to the position solution

– In GNSS hostile environments the

improvements can be very significant

– Improvements are seen in all positioning

modes (Autonomous, RTK, post-processing)

Galileo appears to provide further

incremental benefit

– But the system is currently unhealthy

– At least a few years from a constellation that

will provide significant customer benefit

Questions?

Acknowledgements

Trimble China Team

Trimble Terrasat

Trimble Sunnyvale & Westminster US

Trimble New Zealand

Backups

Beijing – Autonomous Performance

24 Hours data at 1Hz logged

– GPS, GLONASS, Galileo, QZSS & BeiDou

– Antenna located on the top of a building

Re-processed in a PC build of the receiver’s least

squares PVT

– The standard positioning mode is a Kalman filter

which performs better

– Use the Least Square to avoid the filter “hiding” any

issues.

– Reprocessing uses receiver source code with a PC

wrapper to handle the data files.

Evaluate each system and combination of systems

Can use the Klobuchar transmitted Ionospheric

data or the BDS GEO Iono.

In this analysis only single frequency considered.

Truth computed by Trimble’s RTX service

GLONASS Only - Beijing

BeiDou only (with GEO Iono)

GPS Only - Beijing

GPS/GLONASS/QZSS

GPS/GLONASS/BeiDou/QZSS

With BeiDou Iono model

Beijing Data – relative to RTX truth

2D Position Error

3D Position Error