2013 Western Australia Surveying Conference
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Transcript of 2013 Western Australia Surveying Conference
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 …
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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
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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
16.05.2013BeiDou? First Australian results of a combined …
Sky plots for Perth
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BeiDou – Signal Frequencies
BeiDou: (Modernized) GPS:
16.05.2013BeiDou? First Australian results of a combined …
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
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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
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Combined BeiDou + GPS: Increased model strength and availability
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Suitable for e.g.:
Developing and operating mines Agriculture (wheat belt in dark yellow)
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GNSS Satellite Availability in Challenging Environments
16.05.2013
“urban canyons”
open pit mines
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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
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B1 BEIDOU.
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BeiDou + GPS: Real-Time Kinematic (RTK) Positioning
16.05.2013BeiDou? First Australian results of a combined …
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
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Single-frequency RTK ambiguity resolution + positioning results – cut-off elevation: 35 deg
16.05.2013BeiDou? First Australian results of a combined …
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)
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Single-frequency RTK ambiguity resolution + positioning results – cut-off elevation: 35 deg
16.05.2013BeiDou? First Australian results of a combined …
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)
Curtin University is a trademark of Curtin University of TechnologyCRICOS Provider Code 00301J
Single-frequency RTK ambiguity resolution + positioning results – cut-off elevation: 35 deg
16.05.2013BeiDou? First Australian results of a combined …
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)
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Beidou + GPS Attitude Determination
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Determination of the relative orientation
between reference systems
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Beidou + GPS Attitude Determination
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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
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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
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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
16.05.2013BeiDou? First Australian results of a combined …
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More information?
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Contact: GNSS Research Centre, Department of Spatial Sciences, Curtin University
Email: [email protected]
Curtin University is a trademark of Curtin University of TechnologyCRICOS Provider Code 00301J
Thanks for your attention!
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Questions?
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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
16.05.2013BeiDou? First Australian results of a combined …
CUTA (Left; reference) and CUTT (Right; rover) GNSS antennas, baseline distance ~1 km
B1 BEIDOU L1 GPS B1 BEIDOU + L1 GPS
Curtin University is a trademark of Curtin University of TechnologyCRICOS Provider Code 00301J
Single-frequency RTK ambiguity resolution + positioning results – cut-off elevation: 10 deg
16.05.2013BeiDou? First Australian results of a combined …
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-only B1
Curtin University is a trademark of Curtin University of TechnologyCRICOS Provider Code 00301J
Single-frequency RTK ambiguity resolution + positioning results – cut-off elevation: 10 deg
16.05.2013BeiDou? First Australian results of a combined …
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
GPS-only L1
Curtin University is a trademark of Curtin University of TechnologyCRICOS Provider Code 00301J
Single-frequency RTK ambiguity resolution + positioning results – cut-off elevation: 10 deg
16.05.2013BeiDou? First Australian results of a combined …
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