IGARSS2011 OnTheUseOfPO.ppt

On The Use of Polarimetric Orientation for On The Use of Polarimetric Orientation for POLSAR Classification and DecompositionPOLSAR Classification and Decomposition

Hiroshi KimuraGifu University, Japan

IGARSS 2011Vancouver, Canada

July 25, 2011

ContentsContents

Background

Polarization Orientation in Built-up Areas

Method to Discriminate Built-up and Non-

built-up Areas

ALOS PALSAR Experiment

ConclusionＩ IGARSS 2011, Vancouver,

Canada

BackgroundBackground

Ｉ IGARSS 2011, Vancouver, Canada

Freeman&Durden decomposition of ALOS PALSAR　 data (Descend.)Double-bounce, Volume, Surface

From map “Isezaki” by The Geospatial Information Authority of Japan (GSI)

Agricultural field

Built-up Area

Objective: To discriminate built-up and non-built-up areas

Polarization Orientation in Built-up AreasPolarization Orientation in Built-up Areas

• PO angle shift of terrain slopes:

ω : azimuth slope angle,γ : ground range slope angle,φ : radar look angle.

Radar

x (azimuth)

y(range)

V H

k

α

φ

z

φφγωθ

sincostan

tantan

+−−=

• PO angle shift of built-up areas: azimuth slope angle: ω →α , ground range angle: γ =0, radar look angel: φ →π/2−φ .

α: wall orientation angle from the normal of radar beam H. Kimura, “Radar polarization orientation shifts in built-up areas,” IEEE GRSL, vol. 5, no. 2, 2008.

φαθ

cos

tantan

−=

-30 -20 -10 0 10 20 30-40

-20

0

20

40

Wall Orientation Angle: α [°]

SAR

Ori

enta

tion

Ang

le: θ

[°]

φ=45° φ=35°

From L-band Pi-SAR data of Gifu( ) 4Arg *LLRROO−=θ


Method to Discriminate Built-up and Non-built-up AreaMethod to Discriminate Built-up and Non-built-up Area


• Detection of built-up areas facing away from the radar (|α|≥αc)

• Method to discriminate Built-up areas: |θa|>c or |θd|>c. Not built-up but level surface areas: |θa|≤c and |θd|≤c. θa, θd : PO angles from ascending and descending orbits c : PO angle threshold from wall orientation angle threshold αcφα costantan cc =

IlluminationIllumination

cα2 cα2

cα2 cα2

UNDETECTABLE zone of built-up areas

DETECTABLE zone of built-up areas

ASCENDING DESCENDING


In case of SMALL threshold In case of SMALL threshold αc

+ (OR)



=

• NO undetectable zone of built-up area• COMMISSION error (Non-built-up areas are assigned to built-up areas) increases.

• OMSSION error (Built-up areas are assigned to non-built-up areas) decreases.

cα2 cα2

cα2cα2

UNDETECTABLE

DETECTABLE


In case of LARGE threshold In case of LARGE threshold αc

+ (OR)



=

UNDETECTABLE zone

cα2 cα2

cα2 cα2

• Undetectable zone of built-up area exists.• COMMISSION error (Non-built-up areas are assigned to built-up areas) decreases.

• OMSSION error (Built-up areas are assigned to non-built-up areas) increases.

UNDETECTABLE

DETECTABLE

ALOS PALSAR Experiment: PALSAR ScenesALOS PALSAR Experiment: PALSAR Scenes


The Atsugi area: about 50 km south-west from Tokyo

Radar illumination azimuth: 99° (Ascending) 261° (Descending)

Expected αc is 9° (No undetectable zone and the max. αc), then the PO angle threshold c will be 10°.

ALOS PALSAR Experiment: ImagesALOS PALSAR Experiment: Images


Pauli color code Freeman&Durden decomposition PO angle|HH-VV|, |HV|, |HH+VV| Double-bounce, Volume, Surface

−π/4 π/4

Study Area Study Area ( 5.2km by 3.1 km )( 5.2km by 3.1 km )


B3

F3

B2

B1

F2

F1

Google Earth image Map by GSI, Japan

B3

F3

B2

B1

F2

F1© Google Earth

Freeman&Durden DecompositionFreeman&Durden Decomposition


Google Earth image Ascending Descending

B3

F3

B2

B1

F2

F1Double-bounce Volume Surface© Google Earth

H-Alpha SegmentationH-Alpha Segmentation


H

α

Google Earth image Ascending Descending© Google Earth

B3

F3

B2

B1

F2

F1

PO Angle ImagesPO Angle Images


−π/4 π/4 Google Earth image Ascending Descending

© Google Earth

B3

F3

B2

B1

F2

F1

Discrimination ResultsDiscrimination Results


c=5°(αc=5° ) c=10°(αc=9°) c=12°(αc=11°) White: Built-up area, Black: Non-built-up area

B3

F3

B2

B1

F2

F1

Discrimination Results (Built-up areas)Discrimination Results (Built-up areas)


© Google Earth

© Google Earth

© Google Earth

B1

B2

B3

White: Built-up area Black: Non-built-up area

Google Earth image c=5°(αc=5° ) c=10°(αc=9°) c=12°(αc=11°)

Omission errors

Discrimination Results (Non-built-up areas)Discrimination Results (Non-built-up areas)


© Google Earth

© Google Earth

© Google Earth

F1

F2

F3

Commission errors White: Built-up area Black: Non-built-up area

Google Earth image c=5°(αc=5° ) c=10°(αc=9°) c=12°(αc=11°)



Freeman&Durden decomposition of ALOS PALSAR　 data (Descend.)Double-bounce, Volume, Surface

Built-up Areas (white) and non-built-up areas (black) by c=10°(αc=9°).

Agricultural field

Built-up Area



Freeman&Durden decomposition of ALOS PALSAR　 data (Ascend.)Double-bounce, Volume, Surface

Built-up Areas (white) and non-built-up areas (black) by c=10°(αc=9°).

Agricultural field

Built-up Area

ConclusionConclusion


• PO from ascending and descending orbits can be used to discriminate built-up and non-built-up areas.

• Radar illumination direction influences POLSAR data aanlysis.

• The discrimination prevents misleading of POLSAR decomposition and classification. (Volume scattering in urban areas, double bounce in agricultural fields, et al.)

• The expected threshold with no undetectable zone of built-up areas and the maximum number seems to be good, but a further study is required for the best one .

• Slopes should be separated.

Rotation of Coherence Matrix (Yamaguchi)Rotation of Coherence Matrix (Yamaguchi)


BEFORERotation

AFTERRotation

Agricultural fields

Built-up Areas

|HH-VV||HV||HH+VV|

Ascending 　　　　 Descending

|HH-VV||HV||HH+VV|

Ascending 　　　　 Descending


Range Slope Angle (degrees)

PO Angle Shifts of Slopes PO Angle Shifts of Slopes

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