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
either licensed (e.g. SARscape, ENVI), or those
that are freeware (e.g. POLSARpro, RAT) do
not currently help to calculate and develop the
like and cross polarized signatures of various
targets based on the stokes matrix. Also, the
study and classification of urban targets using
polarimetric microwave remote sensing data is
still not very widespread as much as in case of
optical data. Such a polarimetric study of urban
targets, can greatly help in studying the
scattering behaviour of various urban features
like roads, buildings (tall & short), parks, lakes,
open grounds, bridges, agriculture fields
(cultivated and non cultivated), etc, thus helping
in better land use classification studies using
radar data. In the present work, an attempt has
been made to develop a Polarimetric Signature
calculation and visual representation tool named
“POLSIC”, to generate both Co-polarized and
Cross polarized signatures, based on the
calculation of Stokes matrix and the
backscattered power at various ellipticity and
orientation angles. Various urban targets within
a part of Ahmedabad city were chosen,
followed by generation of polarimetric
signatures (both co-pol and cross pol) for each
target using the developed tool. These
polarimetric signatures were then studied and
analyzed in detail.
2. MATERIAL AND METHODS
2.1 Study Area and Data Used:
For this study, a part of Ahmedabad located at
23° 01°33” N / 72° 27°48” E has been chosen.
The city sits on the banks of the River
Sabarmati, in north-central Gujarat. It spans an
area of 205 km? (79.15 square miles). For this
purpose, C band- RADARSAT-2 data
(quadpol, SLC mode), acquired on 18^
December, 2009 has been used. In order to
verify the targets identified in the RADARSAT-
2 data, geocoded, VIR, LISS-4 optical data
(resolution: 5.8 meters) was used, with its date
of acquisition being 16" November, 2004.
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2.2 Development of *Polarimetric Signature
Calculation and Visual Representation
Tool (POLSIC)":
At this stage of tool development, it allows a
new user/researcher ,in the field of polarimetric
signature study, to use the tool as a dynamic
reference and study material, for viewing
studying and analyzing the existing class types
and their polarimetric signatures, including the
stepwise calculations( for both like and cross
polarization case). At the same time it could also
be used to perform all calculations based on
Stokes matrix, by any level of user, save the
same and again use them as a reference next
time. For a given set of amplitude and phase
values, the tool: Calculates Stokes matrix and
backscattered power for both Co-polarization
and Cross polarization cases; Representation of
the same in tabular form on the GUI, with
dynamic generation of 3D Polarimetric
signatures for both cases; The new values can
be saved in the database using the “SAVE
“button. User can “EDIT”, “UPDATE” and
“DELETE” these values from the GUI; For
Polarimetric signatures generated, functions like
zoom in, zoom out, pan, rotate, data view
cursor, colour bar, and legend are provided. The
tool is user friendly and easy to learn.
In order to develop the tool, Visual Studio 2005
has been used as a platform, and a Matlab
component has been developed to generate 3D
plots. The stepwise scientific calculations
carried out for developing the tool include input
of amplitude and phase values (defined in the
GUI), from both, the database, as well as the
user. The phase values are converted from
degree to radians. This is followed by
calculation of real and imaginary parts for the
defined amplitude and phase values. Thereafter
the expressions of Stokes matrix [K] (Eqn.1)
are calculated. Following are the expressions
calculated, by taking input from real and
imaginary values obtained in the first step.
1
S11 = 5 San 1“ + ISl? rk Sun? zr IScl2)
1
$12 = = (Sha? = Saul. + ISl + IS el)
