Polarization Characteristics in Urban Areas
The differences in predominant polarization in urban areas were evaluated using ratio values R_hh, R_vh, and R_vv expressed in Table 2. The ratio value is calculated from the average of a 5 x 5 pixel window. The ratio images are shown in Fig.2. The white color in each image indicates areas where the ratio value is high. The R_hh image showed that the ratio of HH polarization in the residential areas is high compared with in the commercial areas where high-rise buildings exist. The residential areas are divided roughly into areas where the R_hh value is very high and areas where it is not. The R_vh image revealed that the ratio of VH polarization is intricately distributed regardless of low-rise or high-rise building areas. The remarkably low values for buildings in residential areas are found in some areas. The R_vv image revealed that the ratio of VH polarization in residential areas was low, and remarkably high in parts of commercial areas. Higher buildings displayed a higher VV polarization-ratio.

Table 2 Ratio values of predominant polarized intensity

Ratio value	expression	Characteristics
Rhh	HH / Q	Ratio of HH polarized intensity to total polarized intensity
Rvh	VH / Q	Ratio of VH polarized intensity to total polarized intensity
Rvv	VV / Q	Ratio of VV polarized intensity to total polarized intensity

Q = HH + VH + VV; HH,VH,VV: HH,VH,VV polarized intensity



(a) R_hh


(b) R_vh



(c) R_vv

Fig. 2 Images of polarization ratio
Polarization Signature of Buildings
The detailed polarization characteristics were evaluated using the polarization signature of representative areas. These areas labeled Max(R_hh), Max(R_vh), and Max(R_vv) were selected from the pixels which have maximum R_hh, R_vh, and R_vv values, respectively, in the residential and commercial areas. Max(R_hh), Max(R_vh), and Max(R_vv) are shown in Fig.3 (a)-(c), respectively. Both co- and cross-polarization signatures were computed and generated directly from the Stokes Matrix for the selected areas. In this study, the Stokes Matrix is considered to be an average Stokes Matrix within a 5 x 5 pixel window. The signature has 91 samples (-45 to 45 degrees ellipticity angle) and 181 lines (0 to 180 degrees tilt angle). Details of the wave polarization generation can be obtained be referring to Van Zyl et al. (1987) and Zebker (1987). The relationships among the HH, VH, and VV polarized intensity of each area and the maximum received intensity in each case which are computed from co- and cross-polarization data are shown in Fig.4. The co- and cross-polarized signatures of each extracted pixel are shown in Fig.5.

(a) Max(Rhh) in area A	(b) Max(Rvh) in area B
(c) Max(Rvv) in area C
Fig.3 Areas selected from the pixels which have the maximum value of polarization ratios