The RAMSES multi-pass interferometry campaign in X-band

FRINGE 2007Sébastien Angelliaume, Hélène Oriot, Xavier Dupuis

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Outline of the presentation

• The campaign• RAMSES• Imaged Sites

• Processing• SAR processing• trajectory adjustment

• Temporal decorrelation and permanent scatterers in X band HR SAR imagery

• Oil storage tank filling

• Conclusion

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The sensor

ONERA / RAMSES

* P, L, X, Ku : GMTI capabilityX, Ku, Ka : Interferometry capability

•Multi-band•Very high resolution•Polarimetric•Interferometric•Multi-channel

Band P*

0,43GHz

70MHz

V / H

V and H

L*

1,3GHz

200MHz

V / H

V and H

S

3,2GHz

300MHz

V / H

V and H

C

5,3GHz

300MHz

V / H

V and H

X*

9,6GHz

1200MHz

V / H

V and H

Ku*

14,3GHz

1200MHz

V / H

V and H

Ka*

35GHz

1200MHz

V or H

V and H

W

95GHz

500MHz

L or R

L and R

CenterFrequency

Bandwidth

TransmitPolarization

ReceivePolarization

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Salon de Provence• Town• Flat, sloppy and montaneous area

Fos sur Mer• oil storage tank area

Puylaurent•mountaneaous area with a dam

Séchilienne•mountaneous area•landslide

The campaign (1/2)

from november 2005 to november 2006

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The campaign (2/2)

X band

Resolution (HR & VHR) : 1 agility : 0.5m (264 MHz).2 agilities : 0.26m (504 MHz) on La Séchilienne

Incidence angles : 75, 60 and 40°.

Ping pong mode for instantaneous interferometry

Multi-pass airborne interferometry• Each flight composed of 4 to 6 passes with the same configuration• 3 flights with a one day to one week delay• Flights several months apart on Séchilienne

Challenges:• Altitude ambiguity monitoring

• flight precision : performant DGPS/INS on board

• Processing of HR interferograms with non linear trajectories

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Fos sur Mer : instantaneous interferometry

Amplitude image

Interferogram : Ha ≈ 50m

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Salon de Provence : instantaneousinterferometry

Amplitude image

interferogram: Ha ≈ 50m

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Séchilienne : instantaneous interferometry

Amplitude image

Interferogram : Ha ≈ 50m

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SAR Processing

• SAR processing with a common geometry (Pamela processor)• Focusing on DTED-2

Common geometry

P

Master trajectory

Slave trajectory

• Master and slave images processed so that thewavefronts on point P comingfrom M and S are tangencial

M

S

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Results of the processing

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Trajectory refinement

• modelling of the slave trajectory correction by a sum of cosinesfunctions

• Least square minimisation using the unwrapped interferogram

• Processing with the new slave trajectory

0 cm

10 cm

20 cm Example of trajectory refinement

Coherence analysis

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Coherence false color representation

Amplitude image

0 (no coherent) 1 (coherent)

Interferometric coherence

False color representation

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Coherent change detection : nature of the ground (1/4)

20 minutes 2 days

0 (no coherent) 1 (coherent)

Risk ofdecorrelation

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Very High Resolution : Séchilienne area

Coherence :

simultaneous acquisition

Coherence :

Half an hour

Coherence :

10 months

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Very High Resolution : Séchilienne area

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Very High Resolution : Séchilienne area

Coherence representation interferometric representation

10 months between the 2 acquisitions, in X-band

Permanent scatterers visible on 25 cm resolution images

Oil storage area

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Gas storage area

• Données amplitude

Simultaneousinterferogram : Ha ≈ 50 m

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Gas storage area

Interferogram

1 hour

Ambiguity altitude

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Residual interferogram

• Withdraw of oil storage altitude using the simultaneousinterferogram

• Phase variations are due to:• Residual altitude information due to the low ambiguity altitude of

the multi-pass interferogram• Misestimation of the trajectory• Atmospehric artefacts• Changes in the oil storage roofs

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Oil storage area analysis

Radar illumination direction

Range direction

R1 R2

R3 R4

Computation of φA – φC :

Computation of φB – φC

Local measure insensitive to• trajectory mis-estimation

• Atmospheric propagation artefacts

A B C

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Results

• Change detection on R2

• Consistent with ground truth• R2 was being emptied during the acquisition (roof displacement of

the order of 8cm)

• R1, R3 and R4 : no movement

10°2°166°31°Residual phase difference between top of the tank and floating roof

8°62°169°2.9°Residual phase difference between ground and floating roof

R4R3R2R1Tank #

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Conclusion

• Very interesting campaign

• Not completely exploited

• Main results• Coherence analysis for several temporal intervals

• Change detection on oil storage field

• Work is on going to further analyze the oil storage field

• ONERA has developed a new sensor for civilian applications : SETHI

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SETHI

Thank you for your attention …