Precise positioning in multi-GNSS mode

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Precise

positioning in multi-GNSS mode

Cécile Deprez & René Warnant Novembre 2017

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Compatibilities

between GNSS

BeiDou E5a _E6 L2 B2 B3 Lower L-Band L5 E1 L1 B1 Upper L-Band Frequency (Mhz) GPS Galileo BeiDou E5b B1 BeiDou III E5a+b B2

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 More satellites available

Benefits

of multi-GNSS

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BeiDou + Galileo

Addition

of

GNSS

rises

the number of visible

satellites

Galileo BeiDou

4.7 4.8

Mean number of visible satellites/day

GPS

8.7

7.3

Galileo + GPS

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Benefits

of multi-GNSS

• Satellites visible anywhere anytime • Improved satellite geometry

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P

osition

D

ilution

O

f

P

recision

T

he

geometry

of the satellites affects the position precision :

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0 1 2 3 4 5 6 GPS Galileo BDS P DO P 0 1 2 3 4 5 6

E1/L1 E5a/L5 E5b/B2

GPS L1 + Galileo E1 GPS L5 + Galileo E5a Galileo E5b + BeiDou B2

Multi-GNSS

solution

improves

geometry

DOP v

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 New frequencies available

Benefits

of multi-GNSS

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0.20 0.19 0.15 L1 L2 L5 0.24 0.17 B1 B2 0.13 0.16 0.16 0.06

E1 E5a E5b E5a+b

BDS Galileo

GPS Metres

Best precisions

with

Galileo

code signals

New signals = more robust

𝜎

_𝑃𝑂𝑆

= 𝐷𝑂𝑃. 𝜎

_𝑂𝐵𝑆

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Benefits

of multi-GNSS

 Improved precision on position  New frequencies available

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0 1 2 3 GPS Galileo BDS Pr ecisi on on pos it io n (3D RMS) 0 1 2 3

E1/L1 E5a/L5 E5b/B2

Me

tr

es

Multi-GNSS

solution leads to

more precise positions

regardless of the type of receiver used

GPS L1 + Galileo E1 GPS L5 + Galileo E5a Galileo E5b + BeiDou B2

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Benefits

of multi-GNSS

 Improved precision on position  New frequencies available

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Drawbacks

of multi-GNSS

 Differences between GNSS • Coordinate systems • Time systems • Hardware delays

additional biases

negligible estimable constant variable Additional unknown Removed

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ISBs

are

receiver-dependent

University of Liège

Trimble

Septentrio

R9 R9

_x5

xS

_x4

x4

Mixed-receiver

pairs

Identical-receiver

pairs

Mean:

1.52 m

Mean:

0.00 m

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2014 ₂₀₁₅ 2016

ISBs

are

stable

across years

Mean:

2.85 m

Mean:

2.83 m

Mean:

2.85 m

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Firmware updates

for phases

Receiver multipath filter

for codes

ISBs

might be

affected

by

After

Before

After

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Conclusion

 Drawbacks of multi-GNSS • Coordinate systems • Time systems

• Hardware delays _{Constant - Receiver and frequency dependent}

Constant – given in the ephemeris data Negligible

 Benefits of multi-GNSS • Availability

• Position precision improvement • Reliability

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0 1 2 3 4 5 6 7 8

E1/L1 E5a/L5 E5b/B2

M

ulti-GNSS

improves

positioning results

0 1 2 3 4 5 6 7 8 GPS Galileo BDS P DO P P reci sion on p os itio n Obs Metres Metres

Multi-GNSS

ISBs removed

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