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5_IGARSS2011_HU.pdf
Transcript of 5_IGARSS2011_HU.pdf
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Blind Azimuth Phase Elimination for TerraSAR-X ScanSAR InterferometryAlex Zhe Hu, Linlin Ge and Xiaojing LiGeodesy and Earth Observing Systems Group (GEOS),School of Surveying and Spatial Information Systems,The University of New South Wales, Sydney, Australia
Email: [email protected]
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Contents
• Introduction• Methodology• Results and Discussions• Concluding Remarks
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Contents
• Introduction• Methodology• Results and Discussions• Concluding Remarks
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Introduction• ScanSAR Mode
– Burst Mode– Imaging time < a synthetic aperture
ScanSAR Mode
Stripmap Mode
image originally from Infoterra: http://www.infoterra.de
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Introduction• ScanSAR Mode
– Cover multiple swathes– Large range coverage
ScanSAR Mode
Stripmap Mode
image originally from Infoterra: http://www.infoterra.de
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Introduction• ScanSAR Interferometry
– Cover multiple swathes– Large range coverage
– Global DEM– Large-scale Earthquakes
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Introduction• ScanSAR Interferometry
ALOS PALSAR
EnviSATASAR RADARSAT TerraSAR-X
L-band C-band C-band X-band
250–350km 400km 300–500km 150km
100m 75–150m 50–100m up to 16m
Shimada 2007 Ortiz and Zebker 2007
Holzner and Bamler 2002 ?
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Introduction• TerraSAR-X ScanSAR Interferometry
– Distortion and signal loss in azimuth direction after resampling
– Only SLC data available for the public
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Introduction• TerraSAR-X ScanSAR Interferometry
– Distortion and signal loss in azimuth direction after resampling
– Only SLC data available for the public
– Blind Azimuth Phase Elimination
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Contents
• Introduction• Methodology• Results and Discussions• Concluding Remarks
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Methodology• Phase Estimation Strategy
– The simulated burst for compensation should have similar fringe patterns
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Methodology• Brief workflow
Determination of the Compensation Factor
Coarse Initialisation of the Key Parameter
Refining of the Key Parameter
Elimination of the Azimuth Phase
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( ) ( )2 00s expstrip dmj f w
Tτ ττ π τ τ −⎛ ⎞⎡ ⎤= − ⋅ ⎜ ⎟⎣ ⎦ ⎝ ⎠
( ) ( )20exp rect c
scan dmb
Ts j fT
ττ π τ τ⎛ ⎞−⎡ ⎤= − ⋅ ⎜ ⎟⎣ ⎦ ⎝ ⎠
Moving Direction (Azimuth)
Sensor Sensor
Target
Synthetic Aperture
Stripmap
Moving Direction (Azimuth)
Sensor Sensor
Target
Burst Time
ScanSAR
• Determination of the Compensation Factor
Methodology
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Moving Direction (Azimuth)
Sensor Sensor
Target
Synthetic Aperture
Stripmap
Moving Direction (Azimuth)
Sensor Sensor
Target
Burst Time
ScanSAR
• Determination of the Compensation Factor
Methodology
( ) ( ) ( ) ( )0sincstrip strip ref dmc s s T f Tτ τ τ π τ τ= ∗ = ⋅ −⎡ ⎤⎣ ⎦
( ) ( ) ( ) ( ) ( ) ( ){ }2 20 0sinc expscan scan ref b dm b dm c cc s s T f T j f T Tτ τ τ π τ τ π τ τ⎡ ⎤= ∗ = ⋅ − ⋅ − − − −⎡ ⎤⎣ ⎦ ⎣ ⎦
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Moving Direction (Azimuth)
Sensor Sensor
Target
Synthetic Aperture
Stripmap
Moving Direction (Azimuth)
Sensor Sensor
Target
Burst Time
ScanSAR
Methodology
( ) ( ) ( ) ( )0sincstrip strip ref dmc s s T f Tτ τ τ π τ τ= ∗ = ⋅ −⎡ ⎤⎣ ⎦
( ) ( ) ( ) ( ) ( ) ( ){ }2 20 0sinc expscan scan ref b dm b dm c cc s s T f T j f T Tτ τ τ π τ τ π τ τ⎡ ⎤= ∗ = ⋅ − ⋅ − − − −⎡ ⎤⎣ ⎦ ⎣ ⎦
( ) ( ){ }2exp dm cg j f Tτ π τ⎡ ⎤= −⎣ ⎦
• Determination of the Compensation Factor
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Moving Direction (Azimuth)
Sensor Sensor
Target
Synthetic Aperture
Stripmap
Moving Direction (Azimuth)
Sensor Sensor
Target
Burst Time
ScanSAR
( ) ( )
Methodology
{ }2exp dm cg j f Tτ π τ⎡ ⎤= −⎣ ⎦
( ) ( ) ( ) ( ) ( ) ( )0sinc expscan scan ref b dm bc s s g T f T jτ τ τ τ π τ τ φ⎡ ⎤= ∗ ⋅ = ⋅ − ⋅⎡ ⎤⎣ ⎦⎣ ⎦
• Determination of the Compensation Factor
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Methodology• Coarse Initialisation of the Key Parameter
– The compensation factor is a function of burst duration Tb
( ) ( ){ } ( ){ }2 2exp exp 2dm c dm s bg j f T j f T Tτ π τ π τ⎡ ⎤ ⎡ ⎤= − = − −⎣ ⎦ ⎣ ⎦
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Methodology• Coarse Initialisation of the Key Parameter
( ) ( ) ( ) ( ) ( ){ }( ) ( ) ( ){ }
1
1
scan scan ref scan ref
strip ref
c s s F F s F s
F a S W F s
τ τ τ τ τ
ω ω τ
−
−
⎡ ⎤= ∗ = ⋅⎡ ⎤⎣ ⎦ ⎣ ⎦
⎡ ⎤ ⎡ ⎤= ⋅ ∗ ⋅⎣ ⎦ ⎣ ⎦
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Methodology• Coarse Initialisation of the Key Parameter
– time difference between two peaks of sincfunction is determined by Tb
( ) ( ) ( ) ( ) ( ){ }( ) ( ) ( ){ }
1
1
scan scan ref scan ref
strip ref
c s s F F s F s
F a S W F s
τ τ τ τ τ
ω ω τ
−
−
⎡ ⎤= ∗ = ⋅⎡ ⎤⎣ ⎦ ⎣ ⎦
⎡ ⎤ ⎡ ⎤= ⋅ ∗ ⋅⎣ ⎦ ⎣ ⎦
( ) ( ){ } ( ){ } ( )11 sincscan ref strip bb
F F F c F s F S TaT
τ τ ω ω− ⎡ ⎤ ⎡ ⎤⋅ =⎡ ⎤⎣ ⎦ ⎣ ⎦ ⎣ ⎦
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Methodology• Coarse Initialisation of the Key Parameter
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Methodology• Refining of the Key Parameter
– Iteratively approaching to the real value
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Methodology• Comprehensive workflow
Burst N
Calculatinginitial burstduration Tb0
Generatingcompensation
Burst
Computingcorrelation
factor
compensationBurst
Correlationdecreasing?
IncreasingTb
Final compBurst
Y
N
Fittingcorrelation to find the peak
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Contents
• Introduction• Methodology• Results and Discussions• Concluding Remarks
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Information Master Image Slave Image
Acquisition Date 16 February 2010 27 February 2010
Acquisition Start Time 02:56:12 (UTC) 02:56:13 (UTC)
Acquisition Stop Time 02:56:30 (UTC) 02:56:31 (UTC)
Number of Swathes 4 (strip_04 – strip_07)
Number of Bursts 59 (strip_04 – strip_07) 61 (strip_04 – strip_07)
Central Latitude 28.785 ° 28.785 °
Central Longitude 47.514 ° 47.513°
Range Resolution 2.504 (metre) 2.503 (metre)
Azimuth Resolution 18.5 (metre) 18.5 (metre)
Results and Discussions
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Original Bursts
Results and Discussions
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Original Bursts
Compensation Phases
Results and Discussions
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Original Bursts
Compensation Phases
Bursts after azimuth phase elimination
Results and Discussions
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Resampled slave Burst-based interferogram
Results and Discussions
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TerranSAR-X ScanSARInterferogram
ScanSAR Derived Height Value
-Pi Pi 0 300m
Results and Discussions
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ScanSAR Derived DEM
Results and Discussions
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Histogram of the difference
Results and Discussions
Height difference to SRTM DEM-50 50m
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Contents
• Introduction• Methodology• Results and Discussions• Concluding Remarks
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Concluding Remarks• Simplifying the TerraSAR-X ScanSAR
interferometry by making it Stripmap-like• Precise enough to remove the non-linear
azimuth phases• Providing a solution for TerraSAR-X
ScanSAR interferometry starts from SLC data
• Can also be applied to other advanced SAR system with non-linear azimuth phases, such as Spotlight
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Acknowledgement:
The authors are grateful to Infoterra for providing the TerraSAR-X ScanSAR dataset on this research.
The first author also sincerely thanks GEOS and the Faculty of Engineering of UNSW for supporting his scholarship on his PhD study.