Precise Point Positioning: Performances under Ionospheric Scintillations

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Precise Point Positioning

Matthieu Lonchay Performances under Ionospheric Scintillations

Geomatics Unit

New Navigator Seminar 2012

14 June 2012

NGI, The University of Nottingham

University of Nottingham, UK

Nottingham Geospatial Institute

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Project

Geometry

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Project

Geometry

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The Precise Point Positioning – PPP - is an advanced satellite positioning technique

SPP – Standard Point Positioning

... ... ... ) ( _, , i m p p i i m p i p i p i p D T I c t t P       

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Ionospheric Free (IF) model

Precise satellite clock and orbits products Code pseudorange and carrier-phase Tropospheric delay is estimated

IF IF N t t c T D t t c T D P p i IF P p i IF                     ) ( ) ( p i,

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IF IF N t t c T D t t c T D P p i IF P p i IF                     ) ( ) ( p i,

Iterative Least Square Adjustment (LSA)

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0h 1h 2h 6h 12h 18h 24h 0 5 -5 Time [h] Error [m] North error East error Up error

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The PPP suffers from several weaknesses 0h 1h 2h 6h 12h 18h 24h 0 5 -5 Time [h] Error [m] North error East error Up error

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Ionospheric scintillations disrupt satellite signals propagation

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Ionospheric scintillations degrade satellite signals quality

Signal phase fluctuations

Signal delay

Signal amplitude fluctuations

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- Cycle slips

- Ambiguity resolution processes - Additional convergence time - Measurement noise

- Signal power fluctuations - Lost signals

- Geometry troubles - Signal delay

Ionospheric scintillations degrade satellite signals quality

Signal phase fluctuations

Signal delay

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Ionospheric scintillations decrease PPP performances

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PPP performances under ionospheric scintillations can be improved

WP1 – Signals WP3 – Stochasticity WP5 – Ambiguity WP4 – Model WP2 – Geometry WP0 – GNSS Tools

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Project

Geometry

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Ionospheric scintillations reduce the number of available satellites

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No signal

P

POS DOP

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6h 9h 12h 3 4 5 6 7 8 9 10 11 12 Time [h] Satellites No scintillation Scintillations

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6h 9h 12h 3 4 5 6 7 8 9 10 11 12 Time [h] Satellites No scintillation Scintillations

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N E S W 0° 30° 60° NORM0010.11O 09h00m00s UT G01 G03 G06 G07 G16 G18 G19 G21 G22

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Ionospheric scintillations reduce the satellite geometry quality

6h 9h 12h 0 5 10 15 40 Time [h] PDOP No Scintillations Scintillations 6h 9h 12h 0 5 10 15 40 Time [h] PDOP No Scintillations Scintillations

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The high DOP values are not only

involved by the low number of satellites

T1 DOP = 2.36 DOP = 13.78 T2 N E S W 0° 30° 60° N E S W 0° 30° 60°

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T1 T2 47 . 3  N N  0.04 N E S W 0° 30° 60° N E S W 0° 30° 60°

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A conical satellite geometry involves infinite DOP values

0  N 1 1 ˆ ( )   _  N A A Q_x T                         1 sin cos cos sin cos ... ... ... ... 1 sin cos cos sin cos 1 sin cos cos sin cos 2 2 2 2 2 1 1 1 1 1 n n n n n A               

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T1 DOP = 2.36 DOP = 13.78 T2 N E S W 0° 30° 60° N E S W 0° 30° 60°

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T1 T2 T1 DOP = 2.36 DOP = 13.78 T2 N E S W 0° 30° 60° N E S W 0° 30° 60°

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T1 T2 T1 DOP = 2.36 DOP = 13.78 T2 N E S W 0° 30° 60° N E S W 0° 30° 60°

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The combined use of GPS and Galileo

strongly improves the satellite geometry

N E S W 0° 30° 60° MLAT0010.11O 01h23m00s UT

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N E S W 0° 30° 60° MLAT0010.11O 01h23m00s UT

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0h 3h 6h 9h 12h 0 1 2 3 4 5 10 Time [h] PDOP

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0h 3h 6h 9h 12h 0 1 2 3 4 5 10 Time [h] PDOP

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Project - WP2 Geometry - Objectives

Quantify the improvement of PPP’s performances involved by the expanded GPS-Galileo satellite geometry - Precision - Time convergence - Reliability Ionospheric Scintillations

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Project

Geometry

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Ionospheric Scintillations degrade satellite signal quality

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Measurement error

P

POS DOP

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Ionospheric Scintillations degrade receiver measurement precision

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The PPP stochastic model considers receiver measures to be independent

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2 2 1 2 2 2 21 1 12 2 1

...

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n n n n n

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The PPP stochastic model considers receiver measures to be independent

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2 2 2 2 1

...

0

0 ...

...

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0 ..

0

0 ..

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n

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“Everything is related to everything else, but near things are more related than

distant things.”

First law of Geography…

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Satellite signals are affected differently in case of scintillations S1C [dB-Hz] 2h 3h 4h 5h 6h 7h Time [h] 44 45 46 47 47 48 49 44 45 46 47 48 49 S1C [dB-Hz] S1C [dB-Hz]

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Satellite signals are affected differently in case of scintillations N E S W 0° 30° 60° MLAT0010.11O 03h00m00s UT

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Spatial Auto-Correlation (SAC) can be used to generate a new PPP stochastic model

N E S W 0° 30° 60° MLAT0010.11O 03h00m00s UT

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Spatial Auto-Correlation (SAC) can be used to generate a new PPP stochastic model

N E S W 0° 30° 60° MLAT0010.11O 03h00m00s UT

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Spatial Auto-Correlation index are computed on satellite geometry

N E S W 0° 30° 60° MLAT0010.11O 01h23m00s UT 2 ) ( ) )( ( v v v v v v w w N I i i j i ij j i ij j i          ij ij d w  1 i i S C v  1 SAC  SAC  random ‐1 0 1

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Spatial Auto-Correlation is fluctuating 0h 3h 6h 9h 12h -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Time [h] Moran's I

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Perspectives

- Other SAC indices (Geary’C, …) - Realistic simulations

- Tracking error vs. Power signal - …

Spatial Auto-Correlation research will be expanded

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Project

Geometry

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Precise Point Positioning

Matthieu Lonchay – ULg

M.Lonchay@ulg.ac.be

Performances under Ionospheric Scintillations

New Navigator Seminar 2012

14 June 2012

NGI, The University of Nottingham

Marcio Aquino - UoN Craig Hancock - UoN René Warnant - ULg