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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