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Technical Commission VII

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
Professor Anjana Vyas * *, Ms. Bindi Sashtri?
* Faculty of Geomatics & Space Applications, CEPT University, Ahmedabad, Gujarat-380009,
India- “anjanavyas{@cept.ac.in , °shastribindy@gmail.com
Commission VII, WG VII/2
KEY WORDS: RADARSAT-2, Urban targets, Polarimetric Signatures, Stokes matrix, Copol
signature, Crosspol signature
Various urban targets (land use) from Ahmedabad city were chosen, followed by generation of
polarimetric signatures for each target using the developed tool. These polarimetric signatures were
then studied and analyzed in detail. An attempt has been to develop a Polarimetric Signature
Calculation and Visual Representation Tool assigned name "POLSIC", to generate Co-polarized
and Cross polarized signatures, based on the calculation of Stokes Matrix and the backscattered
power at various ellipticity and orientation angles. The input parameters required for the developed
tool, are the amplitude and phase values of all the four polarizations, for each target using any
quadpol radar imagery. In this study, RADARSAT-2 imagery has been used to obtain the amplitude
and phase values of each target, in all four polarization states. Polarimetric signatures were
generated for various urban targets using the developed tool. Vegetated land, built up in the city,
built up within lake, and road were found to have an overall higher polarimetric response
(backscattered power) as compared to grass lawn, fallow land and minimum in case of water body.
Such Polarimetric responses were obtained due to factors like surface roughness and orientation of
the target with respect to the radar look angle. The shape of the signature also indicates the
scattering characteristics.
1. INTRODUCTION the Cross polarized signatures have orthogonal
transmit and receive polarizations [6]. In order
to study the polarization response of various
A Polarimetric SAR system measures the targets, ‘Stokes matrix’ has been used. It is a
backscattered energy of the targets in the scene, concise description of the polarization response
including its polarization state. The interaction of a backscattering object, given in units of
of the transmitted wave with a scattering object power. It is a 4x4 matrix, an array of real
transforms its polarization. Polarization numbers that transforms the Stokes vector of
signature is a graphical representation of the incident wave into Stokes vector of the
backscattered power received from a target, as a — scattered wave, for a specific target illuminated
function of the polarizations of the incident and by a polarimetric radar system. Research
scattered electromagnetic waves. They show the interests in this area of polarimetric study of
backscatter response at all combinations of various features have not reached critical mass
transmit and receive polarizations and are yet and very few polarimetric processing
represented as either co-polarized or cross- software tools are available for various
polarized. Co-polarized signatures have the polarimetric data types. Most of the softwares
same transmit and receive polarizations, while available for processing of polarimetric data are