Precise Point Positioning: Performances under Ionospheric Scintillations

Precise Point Positioning

Matthieu Lonchay Performances under Ionospheric Scintillations

Geomatics Unit

PhD Meeting

19 June 2012

NGI, The University of Nottingham

University of Nottingham, UK

Nottingham Geospatial Institute

Handling

Project

Softwares

Geometry

We installed two Septentrio receivers in the Geophysical Center of Dourbes (RMI)

SWANS Project

Geophysical Center of Dourbes (RMI) Septentrio PolaRx3eG

Very Short Baseline

GioveA and GioveB (E1 – E5) GPS 01/25 (L1 – L5)

1-year data set Brussels

Liège Dourbes

2 m

SWANS Project

Geophysical Center of Dourbes (RMI) Septentrio PolaRx3eG

Very Short Baseline

GioveA and GioveB (E1 – E5) GPS 01/25 (L1 – L5)

1-year data set

We installed two Septentrio receivers in the Geophysical Center of Dourbes (RMI)

We designed a preprocessing method based on this new data set

Clock Slips Compensation

Cycle Slips

Detection Data Quality Assessment

SBF RINEX MATLAB Tools Orbits Observation Geometry RINEX Other …

Handling

Project

Softwares

Geometry

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

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

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

- Cycle slips

- Ambiguity resolution processes - Additional convergence time - Measurement noise

- Signal power fluctuations - Lost signals - Geometry troubles - Signal delay Signal phase fluctuations Signal delay Signal amplitude fluctuations P POS

DOP

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Ionospheric Scintillations involve physical effects on GNSS signals

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

PPP performances under Ionospheric Scintillations can be improved by using several strategies

Handling

Project

Softwares

Geometry

gLAB is a free and open source multipurpose GNSS data processing and analysis software

ESA/gAGE (UPC)

GNSS Data Processing Tool GNSS Data Analysis Tool Support

Multipurpose

Scientific Professional Educational

AgLAB is a MATLAB software which exploits gLAB to process large network data sets

Automatic downloading Processing (SPP/PPP) Output Data Format Report Files Errors Detection 0 1 2 3 4 5 6 7 8 9 x 104 -2 0 2 4 6 8 10 12 N E S W 0° 30° 60°

AgLAB is a MATLAB software which exploits gLAB to process large network data sets

Automatic downloading Processing (SPP/PPP) Output Data Format Report Files

Errors Detection Galileo?

Rinex v3.0?

Triple Frequency Data? Simulated Data Processing?

0 1 2 3 4 5 6 7 8 9 x 104 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 3 4 5 6 7 8 9 x 104 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0 1 2 3 4 5 6 7 8 9 x 104 -0.15 -0.1 -0.05 0 0.05 0.1

Handling

Project

Softwares

Geometry

Signal amplitude fluctuations

Ionospheric Scintillations

No signal

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POS

DOP

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Ionospheric Scintillations

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

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

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

Ionospheric Scintillations reduce the satellite geometry quality

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

Ionospheric Scintillations reduce the satellite geometry quality

The geometric effect of Ionospheric Scintillations is a major effect for satellite positioning

0h 3h 6h 9h 12h 15h 18h 21h 24h 0 5 10 15 20 25 30 35 40 45 50 Time [h] Position Error [m] Edinburgh 324/03

The geometric effect of Ionospheric Scintillations is a major effect for satellite positioning

0h 3h 6h 9h 12h 15h 18h 21h 24h 0 10 20 30 40 50 60 70 80 90 100 Time [h] PDOP 0h 3h 6h 9h 12h 15h 18h 21h 24h 0 5 10 15 Time [h] Satellite tracked

The geometric effect of Ionospheric Scintillations is a major effect for satellite positioning

0h 3h 6h 9h 12h 15h 18h 21h 24h 0 10 20 30 40 50 60 70 80 90 100 Time [h] PDOP 0h 3h 6h 9h 12h 15h 18h 21h 24h 0 5 10 15 Time [h] Satellite tracked

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

Ionospheric Scintillations produce unbalanced satellite geometry

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

High DOP values are not only due to a small number of tracked satellites

T1 T2

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High DOP values are correlated to a normal matrix close to a singular state

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               

Any linear dependence?

A conical satellite geometry drives the DOP to infinite values

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

High DOP values are not only due to a small number of tracked satellites

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

A nearly conical satellite geometry drives the DOP to critical values

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

A nearly conical satellite geometry deteriorates the satellite geometry quality

0 1 2 3 4 5 6 7 8 9 x 104 -20 -10 0 10 20 30 40 50 60 No problem Problem

Ionospheric Scintillations increase the probability to encounter conical satellite geometries

8 10 13 17 21 24 26 27 28 N E S W 0° 30° 60° Nb sat: 9 |N|: 51.3472 PDOP: 1.431 8 16 26 27 N E S W 0° 30° 60° Nb sat: 4 |N|: 0.004485 PDOP: 43.1737

DOY/YY 27960 08 09 10 15 18 21 26 27 28 29 31 N E S W 0° 30° 60° DOY/YY 27960 08 09 10 15 18 21 26 27 28 29 31 N E S W 0° 30° 60° DOY/YY 40470 05 07 09 14 30 N E S W 0° 30° 60°

Coherent Observation Weigthing Scheme

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

The combined use of GPS and Galileo satellites improves the satellite geometry quality

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

The combined use of GPS and Galileo satellites improves the satellite geometry quality

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

The combined use of GPS and Galileo satellites improves the satellite geometry quality

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

The combined use of GPS and Galileo satellites improves the satellite geometry quality

Quantify the improvement of PPP’s performances involved by the expanded GPS-Galileo satellite geometry - Precision - Time convergence - Reliability Ionospheric Scintillations Scintillations/Geometry/WP2/Objectives

Handling

Project

Softwares

Geometry

Signal amplitude fluctuations

Ionospheric Scintillations degrade satellite signal quality

Measurement error

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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/uncorrelated

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The PPP stochastic model considers receiver measures to be independent/uncorrelated

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

distant things.”

First law of Geography…

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]

Satellite Signals are affected differently by Ionospheric Scintillations

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

Satellite Signals are affected differently by Ionospheric Scintillations

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

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

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

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

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

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

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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

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Spatial Auto-Correlation (SAC) is measured by computing SAC indices on satellite geometries

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

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Spatial Auto-Correlation (SAC) is measured by computing SAC indices on satellite geometries

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

Spatial Auto-Correlation (SAC) is fluctuating in time

Perspective 1: several SAC indices exist with their own specificities

Moran’s I Geary’s C

Mantel’s Γ

Getis and Ord’s index LISA tests

Perspective 2: a Least Square Adjustment to fit a polynomial surface on satellite geometries

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Perspective 3: a Principal Components Analysis (PCA) to study the correlation between variables

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Perspective 4: a SAC detection based on other observables

Signal Strength (S1C)

Tracking error (Conker model) ܵ_ସ

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Perspective 5: more realistic simulations with potentially more tracked satellites

Handling

Project

Softwares

Geometry

Precise Point Positioning

Matthieu Lonchay Performances under Ionospheric Scintillations

Geomatics Unit

PhD Meeting

19 June 2012

NGI, The University of Nottingham

University of Nottingham, UK

Nottingham Geospatial Institute