impact of individual gnss antenna calibration used in the epn...
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![Page 1: Impact of Individual GNSS Antenna Calibration Used in the EPN …acc.igs.org/antennas/euref12_EPN_ant_cal.pdf · 2015-11-02 · antenna calibration model. –Receiver antenna calibration](https://reader035.vdocuments.us/reader035/viewer/2022062602/5ee09f9aad6a402d666bc8a7/html5/thumbnails/1.jpg)
EUREF Symposium, Paris, 6-8 June 2012
Impact of Individual GNSS Antenna Calibration Used in
the EPN on PositioningQ. Baire, E. Pottiaux, C. Bruyninx, P. Defraigne,
W. Aerts, J. Legrand, N. Bergeot and J.M. Chevalier
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EUREF Symposium, Paris, 6-8 June 2012
Outline
• Individual antenna calibration methods• Methodology• Precise Point Positioning• Data sets
• Impact on geodetic positioning• Comparison between individual and igs08.atx
calibrations• Comparison between different individual
calibrations
• Summary and conclusions
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EUREF Symposium, Paris, 6-8 June 2012
• The position of a station refers to the Antenna Reference Point (ARP)
Phase Center VariationPhase Center Variation
ARP
Direction of the signal
Real wavefront
Ideal wavefront
• The distance measured refers to the phase center of the antenna
• Phase center offset (PCO): difference between the ARP and the phase center of the antenna
• Phase center variation (PCV): deviation of the phase center with respect to an ideal wavefront
• PCV is elevation and azimuth dependent
PCO
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EUREF Symposium, Paris, 6-8 June 2012
• Robot calibrations
Individual calibration methodsIndividual calibration methods
• Carried outdoor• Use real GNSS signals• Signal treated with a GNSS receiver•Multipath mitigated by the movement of the robot• Used by the IGS to generate type mean calibrations
Geo++Also Ife, SendStadt Berlin
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EUREF Symposium, Paris, 6-8 June 2012
• Anechoic chamber calibrations
Individual calibration methodsIndividual calibration methods
• Anechoic supposed to reduce reflections• Use generated sine wave • Vector Network Analyzer•Multipath mitigated by the chamber Uni-Bonn
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EUREF Symposium, Paris, 6-8 June 2012
• Differences between Geo++ and Uni-Bonn calibration for the same antenna on L 3
Differences of calibrationDifferences of calibration
TRM59800.00 NONE 54099 installed in RTBT
- =
Geo++ Uni-Bonn
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EUREF Symposium, Paris, 6-8 June 2012
• Differences between Geo++ and Uni-Bonn calibration for the same antenna on L 3
Differences of calibrationDifferences of calibration
TRM59800.00 NONE 54099 installed in RTBT
TRM59800.00 NONE 54144 installed in RTBQ
- =
Geo++ Uni-Bonn
- =
Geo++ Uni-Bonn
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EUREF Symposium, Paris, 6-8 June 2012
• The impact on positioning is not direct:–PCO+PCV will affect each satellite differently at each epoch
How to estimate the impact How to estimate the impact on positioningon positioning
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EUREF Symposium, Paris, 6-8 June 2012
A similar approach was followed as the one used by Rebischung et al., 2011:
–Two separate PPP: identical processing options (satellite antenna calibrations, orbits and clocks, etc…), except for the receiver antenna calibration model.
–Receiver antenna calibration model: igs08.atx and individual calibrations.
–Position offset caused by the changed of receiver antenna calibration model: difference between the daily positions obtained by the different PPP
• Final position offset of a station obtained by taking the mean of the daily estimates over the considered data set of that station
Methodology : PPPMethodology : PPP
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EUREF Symposium, Paris, 6-8 June 2012
• Two data sets are analyzed here
–The EPN stations with individual calibration• from the beginning (2003 for the first individual calibration in the EPN) to
April 2011. • compared to the type calibrations from igs08.atx.
–The six antennas installed at ROB• Each of those antenna have been individually calibrated by both GEO++
and Uni-Bonn. • comparing the two calibrations for each antenna.
Methodology : Data setsMethodology : Data sets
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EUREF Symposium, Paris, 6-8 June 2012
• The first set of data :–EPN stations with individual calibration: from 2003 to April 2011. They
are compared to the type calibrations from igs08.atx.
Impact on Geodetic PositioningImpact on Geodetic PositioningIndividual vs igs08.atx type calibrationsIndividual vs igs08.atx type calibrations
• black: antenna/radome pairs with absolute individual calibrations (15.98%)
• green: antenna/radome pairs with true absolute type calibrations (69.26%)
• orange: antenna/radome pairs with absolute calibrations converted from relative values (6.56%)
• red: antenna/radome pairs without absolute calibrations. In this case, the radome is neglected and the calibration values of the antenna with radome 'NONE' is used (8.20%)
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EUREF Symposium, Paris, 6-8 June 2012
Impact on Geodetic PositioningImpact on Geodetic PositioningIndividual vs igs08.atx type calibrationsIndividual vs igs08.atx type calibrations
North
East
Up
• Position jumps for the 53 station/antenna+radome pairs individually calibrated
• Horizontal:• Distribution around 0 mm• Values up to 4 mm
• Vertical:• No clear distribution• Great differences up to 10 mm
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EUREF Symposium, Paris, 6-8 June 2012
Impact on Geodetic PositioningImpact on Geodetic PositioningIndividual vs igs08.atx type calibrationsIndividual vs igs08.atx type calibrations
• Some position biases equal to 0:• Type mean based on 1 individual calibration
• A particular model of antenna, the TRM55971.00 TZGD, is present in 11 stations and with individual calibration
What are the differences between each individual calibration and the type calibration ?
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EUREF Symposium, Paris, 6-8 June 2012
Impact on Geodetic PositioningImpact on Geodetic PositioningIndividual vs igs08.atx type calibrationsIndividual vs igs08.atx type calibrations
• The type calibration is the mean of GEO++ calibration of 8 antennas• All the individual calibration not done by the same institute
• The north component shows differences up to 2 mm with respect to the type calibration
• The up component shows large differences up to 10 mm with respect to the type calibration
SenStadt BerlinIfE LW
a
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EUREF Symposium, Paris, 6-8 June 2012
• The second set of data :–The six antennas installed at ROB. Each of those antenna have been
individually calibrated by both GEO++ and Uni-Bonn. The impact of the calibration method on the positioning is investigated by comparing the two calibrations for each antenna.
•What is the impact of the calibration method on the positioning ?
Impact on Geodetic PositioningImpact on Geodetic PositioningGeo++ vs Uni-BonnGeo++ vs Uni-Bonn
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EUREF Symposium, Paris, 6-8 June 2012
Impact on Geodetic PositioningImpact on Geodetic PositioningGeo++ vs Uni-BonnGeo++ vs Uni-Bonn
One LEIATR25.R3 NONE antennaAll the other antennas are TRM59800.00 NONE antennas.
• No systematic effect on the horizontal component. But significant effect
• Values up to -7 mm. Too few values to evocate a trend
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EUREF Symposium, Paris, 6-8 June 2012
Impact on Geodetic PositioningImpact on Geodetic PositioningGeo++ vs Uni-BonnGeo++ vs Uni-Bonn
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EUREF Symposium, Paris, 6-8 June 2012
Impact on Geodetic PositioningImpact on Geodetic PositioningGeo++ vs Uni-BonnGeo++ vs Uni-Bonn
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EUREF Symposium, Paris, 6-8 June 2012
SummarySummary
• Comparisons between station positions computed with individual and igs08.atx receiver antenna calibrations show that (results for Europe):
–The position offset can reach 4 mm in horizontal component and 10 mm in the vertical component.–The position offsets have a greater impact on the vertical
component.–For the same antenna model, the position offsets induced by
different individual calibrations with respect to igs08.atx calibrations can reach 2 mm in the horizontal component and 10 mm in the vertical component.
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EUREF Symposium, Paris, 6-8 June 2012
SummarySummary
• Individual receiver antenna calibrations from Geo++ and UniBonn show that (results for 6 antennas in Brussels):
–The position offsets can reach 3 mm in the horizontal component and 7 mm in the vertical component.–Position offsets induced by different calibration methods can be
larger than those induced by the difference between an individual and type calibrations.
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EUREF Symposium, Paris, 6-8 June 2012
ConclusionConclusion
• This effect will depend on the latitude of the station:
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EUREF Symposium, Paris, 6-8 June 2012
ConclusionConclusion
• Use of individual calibrations for positioning applications:– physically more relevant than type mean calibrations–can lead to inconsistent results (e.g. IGS use type mean calibrations)
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EUREF Symposium, Paris, 6-8 June 2012
ConclusionConclusion
• Use of individual calibrations for positioning applications:– physically more relevant than type mean calibrations–can lead to inconsistent results (e.g. IGS use type mean calibrations)
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EUREF Symposium, Paris, 6-8 June 2012
ConclusionConclusion
• Difference between individual and type mean calibrations–Nothing on the accuracy on positioning–No clue of an improvement of the repeatability so far
• But–No jumps in the timeseries when the type mean calibration are
updated
Individual calibrations ensure continuity in the timeseries