Phase-difference of urban area in polarimetric SAR images

Proposed is a new phase-difference parameter for classifying urban areas in a polarimetric SAR image. First, the phase-difference characteristics of urban areas was analysed for various orientation angles. Subsequently it was found that the co-polarised phase-difference (CPD) is adequate for an aligned urban area, while the cross-polarised phase-difference (XPD) is the best parameter for a 45 degrees-oriented urban area. Based on these analyses, the CPD was used for a small orientation angle (vertical bar theta vertical bar <= pi/8) and the XPD for a large orientation angle (vertical bar theta vertical bar > pi/8) to improve the accuracy of the urban classification in a polarimetric SAR image. This new technique was verified using polarimetric SAR image data sets (PALSAR and RADARST-2 images).