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Temporal decorrelation analysis at P-band over tropical forest
Sandrine Daniel, Pascale Dubois-Fernandez, Aurélien Arnaubec, Sébastien Angelliaume
IGARSS 2011, Vancouver
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Overview
• TropiSAR Campaign
• Temporal coherence• Methodology• Paracou Analysis
• Tomography
• Conclusion
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Translating objectives into flight scenario
• TropiSAR objectives• Evaluate the BIOMASS mission concept over tropical forests• Provide a dataset for algorithm validation
• Radiometric analysis• Reference plots with range of biomass in the high values• Up to 520 t/ha
• Temporal decorrelation analysis• Identical trajectories flown on different dates (22 days)
• PolInSAR• Vertically shifted trajectories (100ft and 50ft)
• Adequate altitude of ambiguity throughout the swath
• Tomography• Six vertically shifted trajectories • 0 ft, 50ft, 100ft, 150ft, 200ft, 250ft
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TropiSAR: the campaign
the in-situ database CIRAD-EDB
- based on permanent plots managed by Guyafor project - 28 plots – 157 ha - 98200 measured trees, diameter > 10cm- biomass ranging from 100t/ha to 500t + /ha
the SAR database ONERA
- 7 flights over 22 days
the data analysis- CESBIO: radiometry – polarimetry - ONERA: PolInSAR - IRD: Polarimetry- EDB-CIRAD: in-situ error+…..
Under fundings from ESA, CNES and ONERA
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TropiSAR: the sites
Paracou
Arbocel
Nouragues
Rochambeau
Kaw
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TropiSAR: the waveform
24-4724-62Incidence angle range [°]26004000Nb of pixels in range43504350Near Range [m]0.751.0Azimuth pixel spacing [m]0.751.0Range pixel spacing [m]1.01.5Azimut resolution [m]1.01.2Range Resolution [m]1131Relative bandwidth [%]
1250-1400 (B=150 MHz)335-460 (B=125 MHz)Processed Bandwidth [MHz]0.214-0.240.652 – 0.896Processed wave length [m]1250-1400260-460Bandwith [MHz]
500500Sampling rate [MHz]52.5Actual PRF [kHz]
200500Peak Power [W]Full-PolarFull-PolarMode
Waveform120Velocity [m/s]
13000/ 3962Altitude [ft,m]Geometry
L-BandP-BandParameter
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Acquisition geometry
Acquisition Geometry
0
1
2
3
4
0 1000 2000 3000 4000 5000 6000 7000
Distance from Nadir (m)
Alt
itu
de
(km
)
Inc 20° Inc 30° Inc 40° Inc 50° Inc 60°
L Band Useful Swath
P Band Useful Swath
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TropiSAR: August 2009
01-SeptStandardVol 6
30-AugustStandardVol 5
24-AugustTomography ParacouVol 4
17-AugustStandardVol 3
14-AugustTomography NouraguesVol 2
12-AugustStandardVol 1
10-AugustValidation/calibrationVol 0
DateDescriptionTropiSAR
Temporal decorrelation analysis - PolInSAR
Tomography - PolInSAR
22 days
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Database over Paracou
Temporal Shift
Ver
tical
Shi
ft
Flight 0
Flight 1
Flight 2
Flight 3
Flight 4
Flight 5
Flight 6
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TropiSAR: the temporal decorrelation
0 0.10 0.1
2 4 7 14 20 22
kz
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Interferometric coherence wrt temporal baseline
2 days 14 days
4 days
7 days
20 days
22 days
Presented at PolInSAR-2011
Objective: complete the temporal analysis with all possible combinations
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Available temporal baselines over Paracou
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• Systematic methodology
• InSAR Coherence
Temporal Coherence
11
1−+
=SNR
SNRγ
Noise decorrelationTemporal decorrelation
Scattering decorrelation
ZBif 1=kzγ?
tempgeomkzSNRmeas γγγγγ =
• RVoG model )1( ααγγ −+= vkz
∫
∫+
=hv
0
'dcos
'2
hv
0
'd'cos
'2
zz
zzikz
v
e
ez
θσ
θσ
γ
vγminγ
( )0,1
−−ℑ= *
min 1
1v
v
v γγγγ
Spectral shiftNegligible in airborne context
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• Systematic methodology
• InSAR Coherence
Temporal Coherence
11
1−+
=SNR
SNRγ
Noise decorrelationTemporal decorrelation
Scattering decorrelation
ZBif 1=kzγ?
tempgeomkzSNRmeas γγγγγ =
vγminγ
( )0,1
∫
∫+
=hv
0
'dcos
'2
hv
0
'd'cos
'2
zz
zzikz
v
e
ez
θσ
θσ
γ
Spectral shiftNegligible in airborne context
dB/m4.0
m30
45
==
°=
σ
θ
vh
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Temporal Coherence: Paracou
• Correct for SNR contribution
• Compute coherence histogram over Rois f
• Compute histogram peak for γmin>0.95
2 days : Flight 0 - 1 2 days : Flight 1 - 2 2 days : Flight 5 - 6
4 days : Flight 0 - 23 days : Flight 2 - 3 5 days : Flight 1 - 3
6 days : Flight 4 - 5 7 days : Flight 0 - 3 7 days : Flight 3 -4
10 days : Flight 2 - 48 days : Flight 4 - 6 12 days : Flight 1 - 4
13 days : Flight 3 - 5 14 days : Flight 0 - 4 15 days : Flight 3 - 6
18 days : Flight 1 - 516 days : Flight 2 - 5 18 days : Flight 2 - 6
20 days : Flight 0 - 5 20 days : Flight 1 - 6 22 days : Flight 0 - 6
RGB Hh-Hv-Vv
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• Paracou Analysis
Temporal Coherence: Paracou
RGB Hh-Hv-Vv 0.96<γSNR<0.99
95.0min >γ
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Ground elevation estimation under dense forest using P-band T-SAR
LIDARP-Band, Hh Hv Vv T-SAR : P-Hh, N=6, 21x21
-40m 5m
RMSE = 4.4 m
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Conclusions
• Temporal coherence analysis over tropical forests at P-Band
• Systematic analysis was performed to explore if a decreasing trend was visible
• The imperfect trajectories created artefacts in the analysis
• A criteria based on the RVoG model was proposed to select areas with proper kz
• No clear trend was observed and the temporal coherence remains high even for the longest temporal baselines
• Ground elevation estimation under dense forest using P-band T-SAR
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Questions?!?
Temporal decorrelation analysis at P-band over tropical forest
IGARSS 2011, Vancouver