POLinSAR 2007
Frascati, Italy. January 22-26, 2007.
Polarimetry and Persistent Scatterer Interferometry session
Comparison of L- and X-band POLSAR
Data for Characterization of Polarization
Orientation Angle Shift
Induced by Man-made Structure
Koichi IRIBE, Motoyuki SATO, Tohoku University, Japan
41 Kawauchi, Aoba-ku, Sendai, Miyagi Prefecture, 980-8576
iribe@cneas.tohoku.ac.jp
Tel/Fax: +81(22)795-6074
Shift of Polarization Orientation Angle
Induced by Ground Surface Patch
Jong-Sen Lee, Dale L. Schuler, et al.
The induced polarization orientation
angle shift θ is represented,
tan θ =
− tan ω
− tan γ cos φ + sin φ
Where tanω is the azimuth slope,
tanγ is the range slope, φ is the radar look angle.
Induced by Dihedral Structure
Hiroshi Kimura, et al.
tan θ =
− tan α
cos φ
Where tanα is the target azimuth angle,
φ is the radar look angle.
Estimation of
PO Angleθfrom POLSAR data
The Circular Co-Pol method:
*
θ = ⎡⎣ Arg ( ORR OLL
) + π ⎤⎦ 4 For θ > π 4, replace θ by (θ − π 2 )
Where ORR and OLL represent the observed scattering matrix of RR and LL.
Illumination Direction
Azimuth
Large-scale building
X-band, 187.5m*225m,
|HH-VV|, |2HV|, |HH+VV|
Estimated PO Angle θ
Pi-SAR
New R&D for monitoring Earth
Environment.
NiCT and JAXA developed
Pi-SAR in 1996.
Pi-SAR: Airborne High-resolution Multi-parameter SAR
X-band
L-band
Frequency
9.55GHz
1.27GHz
Wave length
3.14cm
23.6cm
Resolution
1.5m
3m
Observation
mode
Polarimetry
[HH/HV/VH/VV]
Interferometry
Polarimetry
[HH/HV/VH/VV]
X-band Main Antenna
X-band Sub Antenna
L-band Antenna
©NiCT/JAXA
Investigation of the frequency dependence.
Objective
Sendai city, February 12, 2005
Illumination Direction
Azimuth
L-band
X-band
The azimuth angle of dihedral structures is an important parameter
which represents the characteristics of Urban area.
Investigate the properties of PO angles from the view point of wavelength.
Polarimetric Analysis of Urban Area
Difficulties, such as layover, shadowing, and multi-bounce, etc.
In addition, our targets are dihedral structures.
A model fit for Urban structures.
A Model fit for Urban Structures
T. Moriyama, et al., 2005
Polarimetric correlation coefficient
S hh S hv* = S hv Svv* = 0
S hh S hv* ≠ 0, S hv Svv* ≠ 0
for natural distributed area.
for urban area.
Scattering Model
(1) Odd-bounce scattering
[ S ]Odd
⎡β
=⎢
⎣0
0⎤
, Re( β ) > 0
⎥
1⎦
where βis a ratio of HH to VV.
(3) Cross scattering
[ S ]Cross
⎡γ
=⎢
⎣ρ
ρ⎤
1 ⎥⎦
(2) Even-bounce scattering
[ S ]Even
⎡α
=⎢
⎣0
0⎤
, Re(α ) < 0
1 ⎥⎦
where αis a ratio of HH to VV.
Wire (Re(γ) >0) or Dihedral structure (Re(γ) <0).
,where γand ρare a ratio of HH and HV to VV.
Algorithm
*
S hh S hh
= f Odd β + f even α + f Cross γ
2
2
2
Svv Svv* = f Odd + f even + f Cross
S hh S
*
vv
Not zero for Urban area
= f Odd β + f evenα + f Cross γ
S hv S hv* = f Cross ρ , Shh S hv* = f Cross γρ * , Shv Svv* = f Cross ρ
2
where fOdd, fEven, and fCross are the odd-bounce, even-bounce, and cross scattering
contributions to <SvvSvv*>, respectively.
If Re( S hv Svv* ) > 0, then α = −1,
If Re( S hv Svv* ) < 0, then β = 1.
Total power P can be decomposed into the three contributions for each scattering model.
P = POdd + PEven + PCross
f Even (1 + α ) for Re(γ ) > 0
2
PEven =
f Even (1 + α ) + f Cross (1 + γ + 2 ρ ) for Re(γ ) < 0
2
2
2
Dihedral Structures in an Image
α ≠0
Target azimuth
angle α = 0
500m*500m
Intensity of (HH-VV).
X-band, HH, HV, VV
PEven
Extraction of Dihedral Structures
HH − VV
Pixel Number
PEven bounce
−2.0[dB]
Intensity Value [dB]
Right upper figure:
Pauli Polarimetric decomposition Image.
HH-VV, 2HV, HH+VV.
Right lower figure:
Binary Image. Threshold: Peven>-2.0[dB]
PO Angle Shifts by Dihedral Structures
PO Angle Shifts
Masked PO Angle Shifts
Built-up Area
Residential block
1250m*1250m
L-band, HH-VV, 2HV, HH+VV
Estimated PO Angle θ
X-band, HH-VV, 2HV, HH+VV
Estimated PO Angle θ
Not Built-up Area
Large-scale buildings
L-band, HH-VV, 2HV, HH+VV
Estimated PO Angle θ
500m*500m
X-band, HH-VV, 2HV, HH+VV
Estimated PO Angle θ
Estimation of Target Azimuth Angle α
Conversion of PO angleθto target azimuth angleα:
α = tan −1 ( − cos φ tan θ )
,where φ is the radar look angle.
Radar look angle φ = 40.5(deg)
L-band, Window Size is 3*3 pixels.
X-band, Window Size is 3*3 pixels.
αmeasure = 23.6(deg)
αmeasure = 12.3(deg)
αmeasure = 39.3(deg)
αmeasure = −1.5(deg)
Estimated target azimuth angleα(deg)
Comparison of Measured and Estimatedα
L-band
x X-band
Measured target azimuth angleα(deg)
Low accuracy for larger target azimuth angleα.
Since the resolution of L- and X-band is 9m and 4.5m respectively,
(window size is 3*3 pixels) X-band is effective for wider range estimation of α?
Summary
•
The azimuth angle of man-made structure is an important parameter
which represents the characteristics of Urban environment.
•
We focused on PO angle shifts induced by dihedral structure formed by a
vertical wall and the ground.
•
We estimated the target azimuth angle from PO angle shift, and
investigated the accuracy of the estimation from the view point of wave
length.
•
As for the estimation of azimuth angle of large-scale buildings, X-band
data of 3*3 pixels window size shows good accuracy.
•
We will change the target and the window size for averaging.