Transcript Document

BeiDou? First Australian results
of BeiDou + GPS positioning
Dennis Odijk, Robert Odolinski, Nandakumaran Nadarajah,
Boris Padovan, Peter Teunissen
GNSS Research Centre, Curtin University
2013 Western Australia Surveying Conference
16.05.2013
Presentation Outline
 BeiDou
What 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
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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
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Sky plots for Perth
BeiDou – Signal Frequencies
BeiDou:
B1:
B2:
B3:
1561.098 MHz
1207.140 MHz
1268.520 MHz
B2
(Modernized) GPS:
19.20 cm
24.83 cm
23.63 cm
L1:
L2:
L5:
B3
1575.420 MHz
1227.600 MHz
1176.450 MHz
19.03 cm
24.42 cm
25.48 cm
B1
BEIDOU
BeiDou, GPS (and Galileo) signals are based on Code Division Multiple Access (CDMA)
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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
Suitable for e.g.:
Developing and operating mines
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Agriculture (wheat belt in dark
yellow)
GNSS Satellite Availability in Challenging
Environments
“urban canyons”
open pit
mines
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BeiDou + GPS: Single Point Positioning (SPP)
B1 BEIDOU.
 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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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
CUTA (Left; reference) and CUTT (Right; rover)
 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 + doubledifferenced phase ambiguities per
constellation
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GNSS antennas, baseline distance ~1 km
Single-frequency RTK ambiguity resolution +
positioning results – cut-off elevation: 35 deg
BeiDou-only B1
System/
Frequency
24 h of data (21/04/13)
Ambiguity resolution
success rate %
for cut-off [deg]
10 15 20 25 30 35
BEIDOU
B1
96.4 96.1 86.9 83.4 66.8 51.5
GPS
L1
79.4 68.9 52.6 33.4 19.3 9.0
COMBINED
B1+L1
98.1 100 100 100 99.4 97.0
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Single-frequency RTK ambiguity resolution +
positioning results – cut-off elevation: 35 deg
GPS-only L1
System/
Frequency
24 h of data (21/04/13)
Ambiguity resolution
success rate %
for cut-off [deg]
10 15 20 25 30 35
BEIDOU
B1
96.4 96.1 86.9 83.4 66.8 51.5
GPS
L1
79.4 68.9 52.6 33.4 19.3 9.0
COMBINED
B1+L1
98.1 100 100 100 99.4 97.0
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Single-frequency RTK ambiguity resolution +
positioning results – cut-off elevation: 35 deg
BeiDou B1 +
GPS L1
System/
Frequency
24 h of data (21/04/13)
Ambiguity resolution
success rate %
for cut-off [deg]
10 15 20 25 30 35
BEIDOU
B1
96.4 96.1 86.9 83.4 66.8 51.5
GPS
L1
79.4 68.9 52.6 33.4 19.3 9.0
COMBINED
B1+L1
98.1 100 100 100 99.4 97.0
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Beidou + GPS Attitude Determination
Determination of the relative orientation
between reference systems
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Beidou + GPS Attitude Determination
24 h of data (17/03/13)
8-m baseline
Instantaneous ambiguity resolution success-rates
LAMBDA: “standard” (RTK) ambiguity resolution; C-LAMBDA: baseline-constrained ambiguity resolution
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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 carrierphase 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
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More information?
Contact: GNSS Research Centre,
Department of Spatial Sciences, Curtin University
Email: [email protected]
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Thanks for your attention!
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
CUTA (Left; reference) and CUTT (Right; rover)
GNSS antennas, baseline distance ~1 km
 Position errors of CUTT :
computed by subtracting
estimated position
from known
coordinates
B1 BEIDOU
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L1 GPS
B1 BEIDOU + L1 GPS
Single-frequency RTK ambiguity resolution +
positioning results – cut-off elevation: 10 deg
BeiDou-only B1
System/
Frequency
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CRICOS Provider Code 00301J
BeiDou? First Australian results of a combined …
Ambiguity resolution
success rate %
for cut-off [deg]
10 15 20 25 30 35
BEIDOU
B1
96.4 96.1 86.9 83.4 66.8 51.5
GPS
L1
79.4 68.9 52.6 33.4 19.3 9.0
COMBINED
B1+L1
98.1 100 100 100 99.4 97.0
16.05.2013
Single-frequency RTK ambiguity resolution +
positioning results – cut-off elevation: 10 deg
GPS-only L1
System/
Frequency
Curtin University is a trademark of Curtin University of Technology
CRICOS Provider Code 00301J
BeiDou? First Australian results of a combined …
Ambiguity resolution
success rate %
for cut-off [deg]
10 15 20 25 30 35
BEIDOU
B1
96.4 96.1 86.9 83.4 66.8 51.5
GPS
L1
79.4 68.9 52.6 33.4 19.3 9.0
COMBINED
B1+L1
98.1 100 100 100 99.4 97.0
16.05.2013
Single-frequency RTK ambiguity resolution +
positioning results – cut-off elevation: 10 deg
BeiDou B1 + GPS L1
System/
Frequency
Curtin University is a trademark of Curtin University of Technology
CRICOS Provider Code 00301J
BeiDou? First Australian results of a combined …
Ambiguity resolution
success rate %
for cut-off [deg]
10 15 20 25 30 35
BEIDOU
B1
96.4 96.1 86.9 83.4 66.8 51.5
GPS
L1
79.4 68.9 52.6 33.4 19.3 9.0
COMBINED
B1+L1
98.1 100 100 100 99.4 97.0
16.05.2013