centre spatial de liège institut montefiore université

8/14/2019 Centre Spatial de Lige Institut Montefiore Universit

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17th DLR-CNES Workshop on Information Extraction and Scene Understanding for Meter Resolution Ima es

GEMITORGEorfrencement Multimodal dImages Tridimensionnelles Optiques et Radar

MULTIMODAL GEOREFERENCING of3D VHR

OPTICAL and X-BAND SAR IMAGERY

Antonella [email protected]

Centre Spatial de LigeInstitut Montefiore

Universit de Lige, Belgium


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OUTLINE

ContextIssuesPhenomenology (review)

Technological approachResultsConclusions

Future work


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Context


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ORFEOOptical and Radar Federated Earth Observation

Very High resolution Optical (PLEIADES) and RADAR (Cosmo-Skymed)modalities possibly acquired simultaneously

Strong need for optical and radar modalities fusion at pixel level to takefull advantage of the ORFEO opportunity

Need for 3D information extraction (InSAR) for georeferencing theradar modality


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To investigate the limitations of current InSAR techniques

To modify/adapt existing algorithms to VHR peculiarities

To test algorithms on simulated Cosmo-SkyMed data

To georeference visible and SAR images in common reference frame

To fuse SAR and optical VHR images at the pixel level

To develop 3D visualization tools (virtual reality)

GEMITORGEorfrencement Multimodal dImages Tridimensionnelles

Optiques et Radar


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Issues


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C-band vs. X-bandAirborne vs. spaceborne

C-band Spaceborne Standard resolution

X-band Airborne Very High Resolution

X-band Spaceborne Very High Resolution


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Simulated data

Tests performed on simulated CosmoSkyMedRAMSES data set:

Airborne SAR interferometric data set (RAMSES =Radar Aroport Multi-Spectral d Etude deSignatures)VHR:

resolution cell azimuth: 0.55 m resolution cell slant range: 0.49 m

Site: Baux de ProvenceSingle polarization (VV)Single-pass

a z

i m u t

h

range


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Geometrical differences betweenspaceborne and airborne SAR acquisitions

Spaceborne SAR(ERS)

Airborne SAR(RAMSES)

SWATH 25 500 Km 10 100 Km

INCIDENTCE ANGLEwrt NORMAL

20 45 deg. 30 85 deg.

DISTANCE SENSOR-CENTER OF THE

EARTH

~ 7 150 Km ~ 6 373 Km

MINIMUN RANGE ~ 840 Km ~ 3,9 Km

PULSE REPETITIONFREQUENCY

~ 1679,79 Hz ~ 148,148 Hz


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VHR images specific characteristics

Some RAMSES images specific characteristics may lead toInSAR processing difficulties and require some specificalgorithmic design:

ShadowingSpecific backscattering & brightnessMan-made features


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Phenomenology (review)


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Shadowing example

Due to the lowdepression angle, in

RAMSES images,shadowing ispredominant withrespect to layoverand foreshortening. a z

i m u t

h

range

S H A D

O W

S H A D

O W

S H A D

O W


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Buildings example

Buildingsrange

a z

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h


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VHR details

At VHR one easily observes:At VHR one easily observes:range

a z

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Road

Parcel limits

Differentcrops

Vehicle

B u i l d i n g s


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Technical approach


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Slave image already coregistered ==> no testing of the coregistration moduleSame Doppler centroid ==> no azimuth filtering

InSAR testing

Testing of CSL InSAR processor using RAMSES interferometric data set


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The testing study of the InSARprocessor was done, using threedifferent pixel averaging (5x5,3x3, 1x1) when generating the

interferometric products.Final goal is to work with theimage at full resolution pixel 1x1(RAMSES 0,55 x 0,49m).

Pixel averaging


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Results


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InSAR processing first results

Fos202208_MS_rad_0.dat# Mode interferometrique :Compensation_IF= distance_dopplerRetard_apres_demod_hard= 0.000000 sBaseline_x= 0.000000 mBaseline_y= -0.1017500mBaseline_z= -0.6046000 m

RAMSES HEADER slave parameters

wrong orbital phase compensation

correct orbital phase compensation

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range


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InSAR processing test samples 1X1 pixel averaging

Amplitude Coherence Interferogram PhaseUnwrapping


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Simulated CosmoSkyMed data

RAMSES data

Pixel averaging 1x1

Pixel averaging 1x1

Pixel averaging 3x3Pixel averaging 5x5

Pixel averaging 3x3 Pixel averaging 5x5

Unwrapped phase test


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Optical image

Amplitude SAR image

Unwrapped phase


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CSL interpolator is based onChirp-Z transformIt allows applying any affinetransform to complex data:

To test the interpolator, weapply a 45 deg. rotation to boththe master and the slave images

Interpolation test (1)

45 deg. -rotated master image example

++=++=

z z z

x x x

C z B x A z

C z B x A x

112

112


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We regenerate an interferogram from rotated image samples


45 deg.-rotated interferogram non-rotated interferogram


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Master and slave images wererotated 45 deg. successively upto 180 deg. to generate the

corresponding interferogram==> Interpolator used 4 timessuccessively


180 deg.-rotated interferogram


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Interferogram differences Histogram of differences


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Current InSAR processorlimitations

Limitations :The phase unwrapping module works well at full resolution(1x1). but other tests will be performed on more complexareas (i.e. urban area)

Improvements :To work at multiple resolutionsTo improve the residues connection algorithm


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Conclusions


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Geometrical differences between airborne andspaceborne acquisitions must be taken into account infuture developments

The CSL InSAR processor is a good basis for theGEMITOR project since:The Chirp-Z transform based interpolator is suitable forhandling VHR SAR dataPhase unwrapping must be adapted to VHR peculiarities


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Future work


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To test (and adapt if required) the SARgeoreferencing routinesTo study optical and radar modality complementary

To bring the optical and SAR modality into the samegeographical reference frame at pixel levelTo visualize the fusion products and all 3Dinformation in 3D stereo


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