Vineet Kumar, Y. S. Rao Centre of Studies in Resources

Comparative Analysis of RISAT-1 and Simulated RADARSAT-2
Hybrid Polarimetric SAR Data for Different Land Features
Vineet Kumar, Y. S. Rao
Centre of Studies in Resources Engineering
Indian Institute of Technology, Bombay
Mumbai-400076
Outline of presentation
Presentation
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Introduction and Objective
Study area and satellite data
Compact polarimetric SAR systems
Stokes Parameters
Methodology
Results
Conclusions
Introduction
• Timely land use land cover (LULC) information is essential for
change detection, planning and management of natural resources.
• Polarimetric SAR imaging is widely studied and accepted as a
powerful tool for earth observation applications.
• Relative performance of Hybrid/Compact polarimetric modes with
full polarimetry is a current axis of research in SAR earth
observation community
Objective:
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to evaluate the comparative performance of real and simulated
hybrid polarimetric spaceborne data for different land features.
Study Area
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Part of Vijayawada city and its surroundings in the Andhra Pradesh, India.
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Location: 16° 31’ N and 80° 39’ E along the Krishna river coast.
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Major land use land cover: agricultural fields, water body, settlement and
sand.
Main crops cultivated (March): Rice, cotton, banana, sugarcane and corn
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Data Sets
Satellite/Parameters
RISAT-1
RADARSAT-2
Date of Acquisition
09-March-2014
11-March-2014
Frequency
C-Band
C-Band
(5.35 GHz)
(5.405 GHz)
Pass
Ascending
Ascending
Look Direction
Left*
Right
Beam Mode
FRS 1
FQ 8
Polarization
RH, RV
HH, HV, VH, VV
Incidence Angle
31.34°
27.20°
Input Resolution
(along x across)
Output Spacing
(Line x Pixel)
3.33 x 2.34
5.2 x 7.6
(m x m)
(m x m)
1.8 x 2.36
4.73 x 4.79
(m x m)
(m x m)
Field Photographs
Cotton
Rice
Banana
Bare field
Compact Polarimetry
• PI/4 mode: Transmit linear polarization at 45-degree orientation, & receive two
orthogonal linear H and V polarizations (Souyris and Mingot, 2002).
• DCP mode: Right or left Circular transmit and receives right or left circular
polarizations (Stacy and Preiss, 2006).
• Hybrid mode: With right or left circular at transmission and two linear
polarization at reception (Raney, 2007).
• Hybrid mode also known as CL-pol or CTLR mode (Circular Transmit Linear
Receive)
PI/4 Mode
Hybrid Mode
Stokes and its Decomposed Parameters
• Stokes parameter provides a way to represent the power density
relationship of electromagnetic waves in RADAR.
• Stokes decomposed/child parameter derived to characterize received
scattered wave.
Stokes Parameters
2
2
< 𝐸𝐻 + 𝐸𝑉 >
𝑔0
𝑔1
< 𝐸𝐻 2 − 𝐸𝑉 2 >
𝑔2 = 2𝑅𝑒 < 𝐸 𝐸 ∗ >
𝐻 𝑉
𝑔3
−2𝐼𝑚 < 𝐸𝐻 𝐸𝑉 ∗ >
Stokes Decomposed Parameters
DoP = 𝑚 =
𝑔1 2 + 𝑔2 2 + 𝑔3 2
𝑔0 2
𝑔3
Chi = 𝜇𝐸 =
𝑔0
Delta = 𝛿 = atan (
CPR = 𝜇𝑐 =
𝑔3
)
𝑔2
𝑔0 − 𝑔3
𝑔0 + 𝑔3
Methodology
RADARSAT-2 and RISAT-1
SLC products
Multilook
Speckle Filtering
Real Hybrid Pol data
(RISAT-1)
Simulated Hybrid Data (RS-2)
C2 Matrix generation
Backscatter Coefficients
(RH, RV ) analysis
Stokes Parameters (g0,
g1, g2, g3) Extraction
Stokes Child Parameters
(m, Chi, Delta, CPR)
Wishart Supervised
Classification
Accuracy assessment
RESULTS
Backscatter Analysis
LULC features RISAT-1
Simulated
Radarsat-2
RISAT-1
Simulated
Radarsat-2
RH (dB)
RH (dB)
RV (dB)
RV (dB)
Banana
-0.23
-5.54
-0.56
-5.18
Cotton
-3.90
-8.86
-4.38
-9.41
Rice
-3.83
-7.91
-6.73
-12.55
Bare Fields
-7.45
-12.93
-7.64
-12.83
Water Body
-12.63
-19.36
-12.46
-18.11
Sand
-6.79
-11.46
-6.91
-11.23
Settlement-1
6.38
-1.30
-2.17
-8.71
Settlement-2
-4.63
-10.95
-5.74
-10.77
Trees
-3.25
-9.68
-3.79
-9.49
Polarization
 Relative difference of 5
to 6 dB in backscatter
coefficients values.
 Settlement-1 is having
very high backscatter
(6.38 dB) in RH pol of
RISAT-1.
Stokes Parameter Analysis
Stokes Decomposed/Child Parameters
Wishart Supervised Classification comparison
RISAT-1 Hybrid Pol
Simulated RS-2 LC
Simulated RS-2 LC
Accuracy Assessment
Conclusions
 Real (RISAT-1) and simulated (RS-2) hybrid polarimetric data are
compared for backscatter, Stokes parameters and classification
analysis.
 RH, RV Backscatter coefficients follows same trend in both the satellite
products with relative difference of 5 to 6 dB
 Stokes and its decomposed parameters values for different feature
class in follows same trend with few exceptions.
 For the given study area Wishart supervised classification of RISAT-1
data shows better classification accuracy over simulated hybrid pol
data.
 This initial study also demonstrates the potential of hybrid polarimetric
data potential for crop and other land feature analysis.
Thank you..
Hybrid Pol System Architecture
• Dual-linearly polarized antenna will radiate circular polarization if the H
and V feeds are driven simultaneously and 90° out of phase.
• Transmitter output passes through a 90° hybrid, whose output feed the Helements and the V-elements, respectively.
• The received data by a dual-linearly-polarized antenna, kept in their linear
bases all the way through to the processor inputs.
Generic hybrid polarity system with circular transmit and dual linear receive configuration (Source;
Raney, 2007)
19
Stokes Parameters without settlement-1 class
Stokes g0
2.5
Stokes g1
0.3
0.25
2
0.2
0.15
1.5
0.1
0.05
1
0
0.5
-0.05
-0.1
0
Banana
Cotton
Rice
Bare
Water
Sand
Settle2
Trees
-0.15
Banana
Stokes g2
0.14
Cotton
Rice
Bare
Water
Sand
Settle2
Trees
Stokes g3
0.2
0.12
0.15
0.1
0.08
0.1
0.06
0.04
0.05
0.02
0
0
-0.02
-0.05
-0.04
-0.06
-0.1
-0.08
Banana Cotton
Rice
Bare
Water
Sand
Settle2
Trees
Banana Cotton
Rice
Bare
Water
Sand
Settle2
Trees
References
Ainsworth, T. L., Kelly, J. P., Lee, J.-S., (2009) “ Classification comparisons between dual-pol, compact
polarimetric and quad-pol SAR imagery”, ISPRS Journal of Photogrammetry and Remote Sensing,
Volume 64, Issue 5, , Pages 464-471.
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C. Champagne , A. Merzouki and T. Geldsetzer, (2010) "Compact polarimetry overview and
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Raney, R. K., (2007), "Hybrid-polarity SAR architecture," IEEE Trans. Geosci. Remote Sens., vol.
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