convergence time improvement of precise point …€¦ · positioning (ppp) requires shorter...
TRANSCRIPT
Mohamed Elsobeiey and Ahmed El-RabbanyDepartment of Civil Engineering (Geomatics Option)
Ryerson University, CANADA
CONVERGENCE TIME IMPROVEMENT OF PRECISE
POINT POSITIONING
Introduction
Impact of Second-order Ionospheric Delay:
- GPS Satellite Orbit
- GPS Satellite Clock Corrections
- PPP solution
Conclusions and Future Outlook
2
Outline
Real-time and near real-time GPS precise pointpositioning (PPP) requires shorter convergence time forthe estimated parameters
Recent research has shown that not all errors andbiases are rigorously modelled in PPP, which results incorrelated residual errors
Such unmodelled errors should be accounted for toachieve shorter convergence of the PPP solution
Second-order ionospheric delays is considered one ofthe most important errors that should be considered inGPS PPP
Introduction
3
Factors Affecting Second-order Ionospheric Delay- Total electron content- Magnetic field at the ionospheric pierce point- Angle between magnetic field
and propagation direction
4
Second-order Ionospheric Delay
X
Y
B0
θPiercePoint
Satellite
hion
Receiverz
z'Z
Rα
Parameters of Geomagnetic Field Magnetic field parameters are estimated at the
Ionospheric Pierce Point (IPP) using the 11th
generation of International Geomagnetic ReferenceField model (IGRF)
Slant Total Electron Content (STEC) P1-P2 is used and satellites and receiver differential
hardware delays are applied
5
Second-order IonosphericDelay (Cont’d)
6
IGS Stations Used in Estimatingorbit and Clock Corrections
7
Effect of Second-order IonosphericDelay on Orbit Determination
GPS Satellite
G02
G03
G04
G05
G06
G07
G08
G09
G10
G11
G12
G13
G14
G15
G16
G17
G18
G19
G20
G21
G22
G23
G24
G26
G27
G28
G29
G30
G31
G32
Orb
it D
iffer
ence
(m)
0.000
0.005
0.010
0.015
0.020
0.025
0.030
Radial Along-trackCross-track
8
Effect of Second-order IonosphericDelay on Clock Corrections
GPS Satellite
G02
G03
G04
G05
G06
G07
G08
G09
G10
G11
G12
G13
G14
G15
G16
G17
G18
G19
G20
G21
G22
G23
G24
G26
G27
G28
G29
G30
G31
G32
Clo
ck R
MS
(ps)
0
10
20
30
40
50
IGS Clock RMSEstimated Clock RMS
NRCan GPS PPP software is modified to accept thesecond-order ionospheric delay correction
The estimated satellite orbit and clock corrections are usedto process the GPS data of several GPS stations
First-order ionosphere-free linear combination of both codeand carrier-phase are used and the correction for thesecond-order ionospheric delay is applied for bothobservables
9
Effect of Second-order IonosphericDelay on PPP Solution
10
IGS Stations Used to Verify the Estimated Orbit and Clock Corrections
11
Latitude Results for StationDRAG – DOY125, 2010
Time (Minutes)0 10 20 30 40 50 60
Latit
ude
Erro
r (m
)
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
First-Order IONO Only First+Second-order IONO
12
Longitude Results for StationDRAG – DOY125, 2010
Time (Minutes)0 10 20 30 40 50 60
Long
itude
Err
or (m
)
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
First-Order IONO Only First+Second-order IONO
13
Height Results for StationDRAG – DOY125, 2010
Time (Minutes)0 10 20 30 40 50 60
Hei
ght E
rror
(m)
-12
-10
-8
-6
-4
-2
0
2
First-Order IONO Only First+Second-order IONO
14
Latitude Results for StationTHA1 – DOY125, 2010
Time (Minutes)0 10 20 30 40 50 60
Latit
ude
Erro
r (m
)
-3
-2
-1
0
1
2
3
First-Order IONO Only First+Second-order IONO
15
Longitude Results for StationTHA1 – DOY125, 2010
Time (Minutes)0 10 20 30 40 50 60
Long
itude
Err
or (m
)
-5
-4
-3
-2
-1
0
1
2
First-Order IONO Only First+Second-order IONO
16
Height Results for StationTHA1 – DOY125, 2010
Time (Minutes)0 10 20 30 40 50 60
Hei
ght E
rror
(m)
-2
-1
0
1
2
3
4
First-Order IONO Only First+Second-order IONO
The impact of the second-order ionosphericdelay on GPS satellite orbit and clockcorrections is investigated
The results showed that an error in the GPSsatellites orbits ranges from 1.5 to 24.7 mm inradial, 2.7 to 18.6 mm in along-track, and 3.2 to15.9 mm in cross-track directions, respectively
Second-order ionospheric-delay can causesatellite clock error up to 0.067 ns (2 cm)
17
Conclusions and Future Outlook
Accounting for the second-order ionospheric delaycan improve the PPP coordinate solution by about 3mm and the convergence time by about 15%
Future research will develop between-satellitesingle-difference (BSSD) algorithm
BSSD PPP with accounting for the second-orderionospheric delay will be the key for carrier-phaseambiguity resolution in PPP
18
Conclusions and Future Outlook(Cont’d)
19
Thank You!