relative positioning with galileo e5 altboc code measurements · relative positioning with galileo...
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Relative positioning with Galileo E5 AltBOC code
measurements
Cécile Deprez
PhD Candidate at the University of Liege
Dissertation submitted to the University of Liège in requirements for a Master’s degree in Geomatics and Geometrology
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• Europe space independenceFull operational GNSS for European citizens
GalileoEuropean Global Navigation Satellite System (GNSS)
• New technologies Atomic clocks, signals, frequencies
• Compatibility and interoperabilityUse combined with GPS (USA), BeiDou (CHN), GLONASS (RUS)
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Constellation
1: In Orbit Validation 2: Full Operational Capability
1999
Launch ofGIOVE-A
Launch ofGIOVE-B
2005 2008
Experimental prototypes
Launch of E11 & E12
Launch ofE19 & E20
2011 2012
IOV1 phase
Launch of E14 & E18
2014 2015 2016
FOC2 phase
FOC2 phaseLaunch ofE26 & E22
Launch ofE24 & E30
Launch ofE08 & E09
Project Initialized
• Full constellation: 30 satellites
• Today: 9 operational satellites
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Signals
Carrier Signals
E1 E1AE1BE1C
E6 E1AE1BE1C
E51 E5a-IE5a-QE5b-IE5b-Q
1: Galileo E5 signal is also called Galileo E5a+b and Galileo E5 AltBOC
10 navigation signals modulated on 4 carrier frequencies
AltBOC Modulation: Improves signal’s resistance
to multipath and provides high code tracking accuracy
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Positioning
Time difference between the reception and the emission time of a signal broadcast from a satellite to a receiver:
cttR i
ppi ).(
Time difference= synchronisation of the clocks
Never reached in practice!
Clock error!
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Position equation
P ip Di
p T ip I i
p M ip,m c(t i tp )
Computing a position
=
At least 4 visible satellites!
Errors
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4 unknowns :
• The 3 components of the receiver position : Xp,Yp,Zp
• The clock error
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Code observable
• Basic observable
• Most common for mass market
• Expected precision: a few metres
• Usually not sufficient for applications that
require decimetres precision
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Observable used by basic receivers
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Hypothesis
Galileo E5 AltBOC outperforms other GPS and Galileo signals:• lower observation noise• better multipath mitigation
Could Galileo E5 AltBOC code measurements be used to reach decimetre-level accuracy
with basic receivers on satellite-based position estimations?
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Double difference :Difference between two receivers’ observations of the two same satellites.
Relative positioning
Principle : Two receivers simultaneouslytrack the same satellites.
P ijAB (t) P i
AB (t) P jAB (t)
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Double difference
Configurations
Zero baseline:
All errors eliminated
Short baseline:
Multipath + Noise errors remaining
Medium baseline:
Multipath + Noise + Atmospheric errors
remaining
0 m 5 m 10 km
10
100 km
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Experimental conditions
Zero/Short baselines:
Medium baselines:
ULg ULg• 2 x Trimble NetR9 • 2 x Septentrio PolaR (X4 & XS)
ULg Waremme• 2 x Septentrio PolaR (X4 & X4TR)
ULg Brussels• 2 x Septentrio PolaRX4
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Zero baseline
GPS L1 Galileo E5a+b
2015, Day Of Year 84 – Septentrio Receivers 12
Position precision : influenced by the number of satellites and their geometry
Observation precision : measure of the precision of the raw incoming signal
Comparison between GPS L1 and Galileo E5 AltBOC
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Zero baseline
Comparison between GPS L1 and Galileo E5 AltBOC
GPS L1 Galileo E5a+b
2015, Day Of Year 84 – Septentrio Receivers 13
Observationprecision:
0,01 m
Position precision:
0,19 m
Observationprecision:
0,09 m
Position precision:
0,26 m
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Short baseline
Comparison between GPS L1 and Galileo E5 AltBOC
2015, Day Of Year 182 – Septentrio Receivers
GPS L1 Galileo E5a+b
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Short baseline
Observationprecision:
0,10 m
Position precision:
1,79 m
Observationprecision:
0,15 m
Position precision:
0,46 m
Statistics
Galileo E1GPS L1
Observationprecision:
0,04 m
Position precision:
0,60 m
Galileo E5
• Galileo E5 shows the best observation precision among all GPS and Galileo signals
• For the present time, the small number of operational Galileo satellites reduces the position precision
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Medium baseline 1ULg -
Waremme25
kilometres
Position precision:
0,40 m
Position precision:
0,88 m
Galileo E5a+b
Statistics
Galileo E5GPS L1
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Medium baseline 2ULg -
Brussels90
kilometres
Position precision:
1,15 m
Position precision:
1,09 m
Galileo E5a+b
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Statistics
Galileo E5GPS L1
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Conclusion
• Observation precisionA few centimetres with all Galileo signals
The best results (GPS, Galileo) are obtained with Galileo E5 AltBOC
• Position precisionA few decimetres with all Galileo signals
The best results (Galileo) are obtained with Galileo E5 AltBOC
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Conclusion
Relative positioning with Galileo E5 AltBOC code measurements should allow
reaching a few decimetres precision on positions with basic receivers up to a
distance of 25 kilometres between receivers.
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Cécile Deprez
PhD Candidate at the University of Liege
Thank you for your attention!