POLARIMETRIC SPECKLE FILTERING - Earth Online · polarimetric speckle filtering should filter all...
Transcript of POLARIMETRIC SPECKLE FILTERING - Earth Online · polarimetric speckle filtering should filter all...
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLARIMETRICSPECKLE FILTERING
POLARIMETRICPOLARIMETRICSPECKLE FILTERINGSPECKLE FILTERING
0
$x
$y( )rE z t,
$z
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
SPECKLE SPECKLE PHENOMENONPHENOMENON
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERINGOBSERVATION POINT
SURFACE ROUGHNESSWAVELENGTH
SCATTERING FROM DISTRIBUTEDSCATTERERS
COHERENT INTERFERENCES OF WAVES SCATTERED FROM MANY RANDOMLY
DISTRIBUTED ELEMENTARY SCATTERERSINSIDE THE RESOLUTION CELL
GRANULAR NOISE
SPECKLE PHENOMENON
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
SPECKLE PHENOMENON
DISTORTION OF THE INTERPRETATION
SPECKLE FILTERING
HOMOGENEOUS AREA HETEROGENEOUS AREA
SPECKLE REDUCTION(RADIOMETRIC RESOLUTION)
DETAILS PRESERVATION(SPATIAL RESOLUTION)
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
SPECKLE REDUCTIONMULTI-LOOK SAR PROCESSING (BoxCar)
Averaging Amplitude / Intensity (Not complex images) ofneighboring pixels
Good Noise Smoothing
Spatial Resolution Loss - blurring edges - erasing thin linesLoss of linear or point features …
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
LINEAR SPECKLE FILTERS
Median FilterMAP Filter (Kuan)Gradient FilterNagao Filter (Nagao)Sigma Filter (Lee)Frost Filter (Frost)Geometrical Filter (Crimmins)Morphological Filter (Safa, Flouzat)
.
.
.
.Local Statistics Filter (Lee 80)
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
SPECKLE : MULTIPLICATIVE NOISE MODEL« SPECKLE is a scattering phenomenon and not a noise.However, from the image SAR processing point of vue, thespeckle can be modeled as multiplicative noise for extended target » (Lee, IGARSS-98)
=
=
=
VVVV
HVHV
HHHH
VV
HV
HH
VV
HV
HH
VV
HV
HH
nxnxnx
xxx
n000n000n
yyy
y
REFLECTIVITYDENSITY
SCATTERINGFIELD
NOISE
pqpqpqpq*pqpqpqpq vXyyY == *
pqpqpqpqpqpq yyYA ==
INTENSITY AMPLITUDE
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
HOMOGENEOUS AREA
NUMBER OF ELEMENTARY SCATTERERS IS IMPORTANT
CENTRAL LIMIT THEOREM
CIRCULARGAUSSIAN
( ) ( )( )( ) ( )
⇒∈⇒+=
==
=
==
212Q
pq2I
pq
Qpq
Ipq
Qpq
Ipq
Q,Ipq
Qpq
Ipqpq
nEnE
0nnE
0nEnE
)21,0(nnnn Νj
NOISE INTENSITY
( ) ( ) ( ) 1vEnnnnv pq2Q
pq2I
pq*pqpqpq =⇒+==
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
HOMOGENEOUS AREA
0pqpq XX =CONSTANT SPATIAL REFLECTIVITY
pqpqpqpqpqpq vXY =
( ) ( ) ( ) 0pqpqpqpqpqpqpqpq XXEvXEYE ===
( ) ( ) ( )pqpq20pqpqpqpqpqpq vvarXvXvarYvar ==
( )( ) ( ) vpqpq
pqpq
pqpqY CVvvar
YEYvar
CV ===
( ) 2YpqpqYv CVvvarCVCV ==
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERINGHOMOGENEOUS AREA N LOOK CASE
INTENSITY AMPLITUDE
COEFFICIENTOF
VARIATION
VARIANCE
MEAN
DENSITY
N LOOK
( ) ( )
N523.01
)N()N(NCV
N1CV
)N()N(N
NX)Avar(
NX)Yvar(
)N()N(
NX)A(EX)Y(E
eX)N(AN2X/APe
X)N(YNX/YP
YN1AY
N1Y
yyAyyY
212
2
NANY
2212
020
21
00
XNA
N0
1N2N
0NAXNY
N0
1NN
0NY
ii
ii
*pqpqpqpq
*pqpqpqpq
0
2
0
≈−+
==
+−==
+==
==
==
==
−−−−
∑∑
ΓΓ
ΓΓ
ΓΓ
ΓΓ
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
LOCAL STATISTICS LINEAR FILTER
( ) j,iYj,ij,i YbaYbYEaX +=+= µ
222XY EXEEYXY νµµµν ν ===with:
( ) ( )1CVEYYvarCV 2Y
2Y
22Y
2Y +== µ
µ
M.M.S.E ( )( )
2j,ij,ib,a
XXEJmin\b,a −=
)Yvar()Xvar(b0
bJb1a0
aJ
νν
µ∂∂
µ∂∂ =⇒=−=⇒=
( )νµµµµµ b21EXEYba2ab2aJ 222YX
2Y
2Y
2 −++−+=
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
( ))Y(EYb)Y(EX j,ij,i −+=νµ
2Y
2X
CVCV1
)Yvar()Xvar(b
νν µ
µ ==
( )
( ) ( )( )1CV
CVCVCVCVEv
CVCVEvEv
EY1EXCV
2v
2v
2Y2
v2Y2
2v
2v
2Y22
X
2Y
2v
2Y
2
2
2X
2X
2X
22X
+−
=−=
−=
−=
−=
µµµ
µµ
µµµ
with:
and:
( )22Y
22Y
CV1CVCVCV1
)Yvar()Xvar(b
ν
ν
νν µ
µ+−
==
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
SPECKLE FILTERINGSPECKLE FILTERING
1)(E == ννµor:
( )
[ ] [ ]2v2v
2
2v
2Y
2v
2Y
j,ij,i
1)Yvar()Y(E)Yvar(
CV1CVCVCV
)Yvar()Xvar(k
)Y(EYk)Y(EX
σσ
+−
=+−
==
−+=
LOCAL STATISTICS LINEAR FILTER
( ) ( ) )Y(EYEYvar,)Y(E 222 −=LOCAL STATISTICS
( )N1CVvvar 2
Y2v ===σA PRIORI INFORMATION
IMAGE NUMBER OF LOOK
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERINGVECTORIAL SPECKLE FILTER
[ ] [ $ ] $ $* *C yy C xxT T= =FILTER
COVARIANCE MATRIX
LOPES - GOZE - NEZRY - TOUZY (1990 - 1992) and SERY (1997) FILTERS, LEE FILTER (1997)
POLARIMETRIC SPECKLE FILTERING SHOULD FILTER ALL ELEMENTS OF THECOVARIANCE MATRIX
AVOIDING CROSS-TALK BETWEEN CHANNELS DUE TO THE FILTERING PROCESS
PRESERVING POLARIMETRIC INFORMATION AND THE STATISTICALCORRELATION BETWEEN THE CHANNELS
PRESERVING SPATIAL RESOLUTION, FEATURES, EDGE SHARPNESSAND POINT TARGETS
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
EXTENSION OF THE LOCAL STATISTICLINEAR FILTER
VECTORIZATION OF THE COVARIANCE MATRIX
[ ]
=⇒==
VVVV
HVVV
HVHV
HHVV
HHHV
HHHH
VVVV
*
HVVV
*
HHVV
HVVVHVHV
*
HVHV
HHVVHHHVHHHH*T
YYYYYY
YYYYYYYYYY
yyC
VECTORIAL MULTIPLICATIVE MODEL
[ ]XVY =
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
VECTORIAL MULTIPLICATIVE MODEL
[ ]XVY =
==
VVVV
HVVV
HVHV
HHVV
HHHV
HHHH
VVVV
HVVVV
HVHV
HHVV
HHHV
HHHH
VVVV
HVVV
HVHV
HHVV
HHHV
HHHH
XXXXXX
v000000v000000v000000v000000v000000v
YYYYYY
Y
VECTORIAL LOCAL STATISTICS LINEAR FILTER
[ ] ( ) [ ]YBYEAX +=
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
M.M.S.E[ ] [ ]( )
[ ][ ]( )( ) ( )[ ]*T2
B,AXXXXEXXEJmin\B,A −−=−=
[ ] [ ] [ ] [ ] [ ]( )
[ ] [ ] ( ) [ ]( ) ( )YcovVEXcovB0BJ
VEBIdA0AJ
1*T −=⇒=
−=⇒=
∂∂∂∂
( ) [ ] ( )( )
[ ] ( ) [ ]( ) ( )YcovVEXcovk
YYEkYEX
1*T −=
−−=
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
VECTORIAL LOCAL STATISTICS LINEAR FILTER
( ) [ ] ( )( )
[ ] ( ) [ ]( ) ( )YcovVEXcovk
YYEkYEX
1*T −=
−−=
DERIVATION AND COMPUTATION OF THE COV(X) MATRIX IS RATHERCOMPLICATED (ILL-CONDITIONING)
IN THE COVARIANCE MATRIX, THE CO-POL INTENSITIES CHANNELSCAN BE MODELED AS MULTIPLICATIVE NOISE MODEL.
BUT THE CROSS-POL (OFF-DIAGONAL) INTENSITIES CHANNELS AREDIFFICULT TO DEFINE : NEITHER MULTIPLICATIVE NOR ADDITIVE
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
10n
0
0.5
1
1.5
2
2.5
3
3.5
4
HVVV r (Nwin = 7)
-10 -5 0 5 100
1
2
3
4
5
6
7
8
9
10
10n
0
0.5
1
1.5
2
2.5
3
3.5
4HHHH (Nwin = 7)
ECAR
T TY
PE
0 2 4 6 8 100
1
2
3
4
5
6
7
8
9
1010n
0
0.5
1
1.5
2
2.5
3
3.5
4HVHV (Nwin = 7)
ECAR
T TY
PE
0 2 4 6 8 100
1
2
3
4
5
6
7
8
9
1010n
0
0.5
1
1.5
2
2.5
3
3.5
4VVVV (Nwin = 7)
MOYENNE
ECAR
T TY
PE
0 2 4 6 8 100
1
2
3
4
5
6
7
8
9
10
10n
0
0.5
1
1.5
2
2.5
3
3.5
4
HHHVr (Nwin = 7)
ECAR
T TY
PE
-10 -5 0 5 100
1
2
3
4
5
6
7
8
9
1010n
0
0.5
1
1.5
2
2.5
3
3.5
4
HHVVr (Nwin = 7)
ECAR
T TY
PE
-10 -5 0 5 100
1
2
3
4
5
6
7
8
9
10
10n
0
0.5
1
1.5
2
2.5
3
3.5
4
HHHVi (Nwin = 7)
-10 -5 0 5 100
1
2
3
4
5
6
7
8
9
1010n
0
0.5
1
1.5
2
2.5
3
3.5
4
HHVVi (Nwin = 7)
ECAR
T TY
PE
-10 -5 0 5 100
1
2
3
4
5
6
7
8
9
1010n
0
0.5
1
1.5
2
2.5
3
3.5
4
HVVV i (Nwin = 7)
-10 -5 0 5 100
1
2
3
4
5
6
7
8
9
10
HHHH
HHHVr
HHHVi
VVVV
HVVVr
HVVVi
HVHV
HHVVr
HHVVi
1/N
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
POLARIMETRIC VECTORIAL SPECKLE FILTER
[ ] T*xxC =[ ] [ ]( ) [ ]( ) [ ][ ]CCEkCEC −−=[ ] T*yyC =
VVVVHVHVHHHHS YY2YS ++=
SPAN IMAGE
( )( ) [ ]2v2
SS
2v
2SS
S 1CV
CV
Svar
Svark
σ
σ
+
−==
LINEAR SCALARLEE FILTER( ) ( )[ ]SSS SSEkSES −−=
J.S. LEE
Homogeneous Areas( ) ( )SSES0k0Svar =⇒=⇒≈
Highly Inhomogeneous Areas( ) ( ) Ss SS1kSvarSvar =⇒=⇒a
REFINED FILTER
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
POLARIMETRIC VECTORIALSPECKLE LEE FILTER
[ ] [ ]( ) [ ]( ) [ ][ ]CCEkCEC −−=
EACH ELEMENT OF THE COVARIANCE MATRIX IS FILTERED
BY THE SAME AMOUNT AVOIDING CROSS-TALK AND PRESERVINGPOLARIMETRIC INFORMATION AND CORRELATIONS
SIMILAR TO THE MULTI LOOK PROCESSING BY AVERAGING THECOVARIANCE MATRICES OF NEIGHBORING PIXELS
BY WEIGHTING THE COVARIANCE MATRIX OF THE CENTER PIXELOF THE SLIDING WINDOW WITH THE MEAN OF COVARIANCE MATRICES FROM SELECTED NEIGHBORING PIXELS PRESERVINGSPATIAL RESOLUTION, FEATURES, EDGES … REFINED LEE FILTER
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
EDGE DIRECTED WINDOW 10
LOCAL HETEROGENEITY &NOISY EDGE BOUDARIES
THE EDGE DIRECTED WINDOWS ARE USED TO
COMPUTE THE LOCAL MEANAND VARIANCE
DIRECTION 1 DIRECTION 2 DIRECTION 3 DIRECTION 4
DIRECTION 5 DIRECTION 6 DIRECTION 7 DIRECTION 8
POLARIMETRIC LEE FILTER
[ ] [ ]( ) [ ]( ) [ ][ ]( )( ) [ ]2v2
S
2v
2S
S 1CVCV
SvarSvark
CCEkCEC
S
S
σσ+
−==
−−=
FOR EACH PIXEL, THE k VALUE IS COMPUTED IN AN EDGE DIRECTED WINDOW
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
OPOP--AIRFIELD LAIRFIELD L--BandBand
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
POLARIMETRIC SPECKLE FILTERING IS NOT AN EXACT SCIENCESUBJECTIVE, IMAGE DEPENDENT
Quantitative Criteria (J.S. Lee - IGARSS 98)
Speckle Reduction (E.N.L)
Edge Sharpness Preservation
Line and Point Target Contrast Preservation
Retention of Mean Values in Homogeneous Regions
Retention of Texture Information
Retention of Polarimetric Information (co, cross-correlations)
Computational Efficiency
Implementation Complexity
THE POLARIMETRIC SPECKLE LEE FILTERIS TODAY A GOOD COMPROMISE
[ ] [ ]( ) [ ]( ) [ ][ ]CCEkCEC −−=
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
POLSAR SPECKLE FILTERINGPOLSAR SPECKLE FILTERING
[ ] [ $ ] $ $* *C yy C xxT T= =FILTER
AVERAGING DATA
SECOND ORDER STATISTICS
COVARIANCE / COHERENCY MATRICES
SMOOTHING AVERAGING
CONCEPT OF THE
DISTRIBUTED TARGETDISTRIBUTED TARGET
© E. Pottier, L. Ferro-Famil (01/2004)
SAPHIR
SAPHIR
Questions ?Questions ?