2013 Western Australia Surveying Conference 16.05.2013 BeiDou? First Australian results of BeiDou +...

2013 Western Australia Surveying Conference 16.05.2013

BeiDou? First Australian results of BeiDou + GPS positioningDennis Odijk, Robert Odolinski, Nandakumaran Nadarajah, Boris Padovan, Peter Teunissen

GNSS Research Centre, Curtin University

Curtin University is a trademark of Curtin University of TechnologyCRICOS Provider Code 00301J

Presentation Outline

BeiDouWhat is it?

Constellation + Signals

Time and Coordinate Systems

First ever results of Beidou+GPS, computed by GNSS Research Centre:

Single Point Positioning (SPP)

Real-Time Kinematic Positioning (RTK)

Attitude determination (Pitch, Roll and Yaw)

Conclusions

16.05.2013BeiDou? First Australian results of a combined …


BeiDou – What is it?

北斗 Big Dipper or Plough, Northern Dipper

Chinese satellite navigation system

Demonstration system (BeiDou-1) completed in 2003

Second generation under construction (BeiDou-2; previously known as COMPASS)

SIS ICD released in December 2012

BeiDou signals will be free of charge

Full global constellation expected in 2020



BeiDou – Constellation

Operational constellation:• 35 satellites (GPS currently 31 - MEO)

• 5 Geosynchronous Earth Obiter (GEO)

• 3 Inclined GeoSynchronous Orbiter (IGSO)

• 27 Medium Earth Orbiter (MEO)

• Global coverage

Current (2013) Constellation:• 14 satellites

• 5 GEO, 5 IGSO and 4 MEO satellites

• Fully operational in the Asia Pacific region


Sky plots for Perth


BeiDou – Signal Frequencies

BeiDou: (Modernized) GPS:


B1: 1561.098 MHz 19.20 cmB2: 1207.140 MHz 24.83 cmB3: 1268.520 MHz 23.63 cm

L1: 1575.420 MHz 19.03 cmL2: 1227.600 MHz 24.42 cmL5: 1176.450 MHz 25.48 cm

BeiDou, GPS (and Galileo) signals are based on Code Division Multiple Access (CDMA)

BEIDOU

B1B3B2


BeiDou – Time and Coordinate Systems

BeiDou Time System:Beidou time (BDT) is synchronized with UTC within 100 ns

Offset BDT and GPS time (GPST)/Galileo time (GST) is broadcast by satellites

BeiDou Coordinate System:BeiDou uses China Geodetic System 2000 (CGS2000)

Coincides with ITRF at few centimetre level; for most (surveying) applications difference between CGS2000 and ITRF can be ignored



Combined BeiDou + GPS: Increased model strength and availability


Suitable for e.g.:

Developing and operating mines Agriculture (wheat belt in dark yellow)


GNSS Satellite Availability in Challenging Environments

16.05.2013

“urban canyons”

open pit mines

BeiDou? First Australian results of a combined …


BeiDou + GPS: Single Point Positioning (SPP)

24 h of data (07/07/12) tracked at Curtin’s permanent GNSS station (Trimble NetR9)

Single-frequency Beidou (B1 code) + GPS (L1 C/A code) data used; cut off = 10 deg

Satellite orbits/clocks from nav. message

Estimate parameters: 3D position + 1 receiver clock error per constellation

Position errors computed by subtracting estimated position from known coordinates


B1 BEIDOU.


BeiDou + GPS: Real-Time Kinematic (RTK) Positioning


Relative (2 receivers) positioning based on code (pseudorange) and carrier phase

Integer carrier-phase ambiguity resolution (IAR) = key to high-precision (mm-cm level) positioning

Short baseline: elimination of clocks + atmospheric errors

Most challenging: single-frequency BeiDou (B1 code) + GPS (L1 C/A code) single-epoch RTK

Double-differenced observations with unknown parameters: 3D relative position + double-differenced phase ambiguities per constellation

CUTA (Left; reference) and CUTT (Right; rover) GNSS antennas, baseline distance ~1 km


Single-frequency RTK ambiguity resolution + positioning results – cut-off elevation: 35 deg


BeiDou-only B1

System/ Ambiguity resolutionFrequency success rate % for cut-off [deg] 10 15 20 25 30 35BEIDOU B1 96.4 96.1 86.9 83.4 66.8 51.5GPS L1 79.4 68.9 52.6 33.4 19.3 9.0COMBINED B1+L1 98.1 100 100 100 99.4 97.024 h of data (21/04/13)




GPS-only L1

System/ Ambiguity resolutionFrequency success rate % for cut-off [deg] 10 15 20 25 30 35BEIDOU B1 96.4 96.1 86.9 83.4 66.8 51.5GPS L1 79.4 68.9 52.6 33.4 19.3 9.0COMBINED B1+L1 98.1 100 100 100 99.4 97.024 h of data (21/04/13)




System/ Ambiguity resolutionFrequency success rate % for cut-off [deg] 10 15 20 25 30 35BEIDOU B1 96.4 96.1 86.9 83.4 66.8 51.5GPS L1 79.4 68.9 52.6 33.4 19.3 9.0COMBINED B1+L1 98.1 100 100 100 99.4 97.0

BeiDou B1 + GPS L1

24 h of data (21/04/13)


Beidou + GPS Attitude Determination


Determination of the relative orientation

between reference systems


Beidou + GPS Attitude Determination


Instantaneous ambiguity resolution success-rates

LAMBDA: “standard” (RTK) ambiguity resolution; C-LAMBDA: baseline-constrained ambiguity resolution

24 h of data (17/03/13)8-m baseline


Conclusions

BeiDou is now operational in Asia-Pacific region and signals can be tracked by multi-GNSS receivers

Combined BeiDou+GPS: increased availability of satellites and frequencies

Data quality BeiDou ≈ GPS

First ever Australian combined BeiDou+GPS results were presented, computed using in-house software of Curtin’s GNSS Research Centre

Combined Beidou+GPS seems to be much more robust for single-frequency RTK positioning and attitude determination in challenging environments, compared to one constellation



Acknowledgments

This work has been executed in the framework of the CRC-SI Positioning Program Project 1.01 ”New carrier-phase processing strategies for achieving precise and reliable multi-satellite multi-frequency GNSS/RSS positioning in Australia”

Curtin PhD student Mr Robert Odolinski ([email protected]) for processing the SPP and RTK examples

Curtin researcher Dr Nanthi Nadarajah ([email protected]) for processing the attitude examples



More information?


Contact: GNSS Research Centre, Department of Spatial Sciences, Curtin University

Email: [email protected]


Thanks for your attention!


Questions?


BeiDou + GPS: “DGNSS” Positioning

Relative (2 receivers) code (pseudorange) based positioning

Short baselines: reduction/elimination of orbit, clock + atmospheric errors

Single-frequency BeiDou (B1 code) + GPS (L1 C/A code) data used

Double-differenced observations with unknown parameters: 3D relative position

Position errors of CUTT :

computed by subtracting estimated position from known coordinates


CUTA (Left; reference) and CUTT (Right; rover) GNSS antennas, baseline distance ~1 km

B1 BEIDOU L1 GPS B1 BEIDOU + L1 GPS





BeiDou-only B1





GPS-only L1





BeiDou B1 + GPS L1

2013 Western Australia Surveying Conference 16.05.2013 BeiDou? First Australian results of BeiDou +...

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