1. Potential Assessment of SAR in Compact and
Full Polarimetry Mode for Snow Detection
Gulab Singh, Yoshio Yamaguchi, Sang-Eun Park Gopalan Venkataraman
Niigata University, Japan IIT Bombay, India
2. Outline
• Introduction
• SAR Measurements
• Snow monitoring methods
• Study Area: Part of Himalayan Snow and Glacier Covered
Region
• Summary
3. Introduction: previous studies
[1] J. C. Souyris, et. al., “Compact polarimetry based on symmetry properties of geophysical media: The π/4 mode,” IEEE
TGRS, vol. 43, no. 3, pp. 634–646, Mar. 2005.
[2] R. K. Raney, “Dual polarized SAR and Stokes parameters,” IEEE GRSL., vol. 3, no. 3, pp. 317–319, Jul. 2006
[3] R. K. Raney, “Hybrid-polarity SAR architecture”, IEEE TGRS, vol 45, no. 11, pp. 3397-3404, 2007.
[4] P. Dubois-Fernandez, et. al., “Compact polarimetry at low frequency”, IEEE TGRS vol. 46, no. 10, pp. 3208–3221, 2008
Applications in land parameters estimation over flat terrain /region
[5] M. Lavalle, “Full and Compact Polarimetric Radar Interferometry for Vegetation Remote Sensing”, Ph.D. Thesis,
Université de Rennes 1, France, 2009.
[6] T. L. Ainsworth, J. P. Kelly and J.-S. Lee, “Classification comparisons between dual-pol, compact polarimetric and
quad-pol SAR imagery”, ISPRS Journal of Photogrammetry and Remote Sensing, 64, pp. 464-471, 2009.
[7] F.J. Charbonneau, B. Brisco, R.K. Raney, H. McNairn, et. al., “ Compact Polarimetry overview and applications
assessment”, Can. J. Remote Sensing, vol. 36, no. S2, pp. S298-S315, 2010.
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[8] S. R. Cloude, Polarisation: Applications in Remote Sensing. London, U.K.: Oxford Univ. Press, 2009
The compact assumptions in [1],[4]-[6] do not apply to scattering from sloped terrain [2],[3],[7] ,
hybrid system 3-dB loss in the radar signal , mismatching the transmitter and receiver polarization basis
the system and theoretical justification issues
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out of several land parameters ……… snow……………
4. SASE Observatory at Solang, Himachal
Snowfall SASE HQ
19-01-2006
Snow parameters in
mountain areas are
particularly sensitive to
changes in environmental
conditions.
Timely information about snow parameters and
their temporal and spatial variability represents
a significant contribution in climatology, local
weather, avalanche forecasting and for the
hydropower production in high mountainous
areas.
5. Ground-based method represents only
exact location measurements of field
observations which may not be
representative of a large area or basin.
20-01-2009
Snow covered : gentle slope
Due to the strong spatial and time 23-01-2009
dependent dynamics of snow cover,
frequent observation cycles are necessary.
Snow free : Steep Slope
Snow covered: River (Solang Nala) Bank, Himachal
6. SAR interaction with snowpack
SAR
Air/snow interface
snow
snow/ground interface
Ground
9. SAR measurements
Single Polarization (ERS-1/2,JERS/PALSAR, Radarsat-1/2, ASAR, TSX)
Dual -Polarization (ASAR, PALSAR, TSX, Radarsat-2)
Quad Polarization (PALSAR, TSX, Radarsat-2)
Compact Polarization (MiniSAR/Chandrayaan-1)(Hybrid C-L)
a few satellites are planned by leading space agencies
for earth observations
Snow/ice monitoring ??
10. • With the quad polarization capabilities, newer
generation spaceborne SAR sensors are
expected to lead significant improvements in
easily snow identification based on microwave
scattering mechanisms
24-05-2010 AVNIR-2 06-06-2010 PALSAR
11. • Is SAR acquisition in quad polarization
advantageous as compared to SAR acquisition
in single, dual and hybrid polarization for
monitoring snow cover in mountainous area
(Himalayas)?
15. Problem with single/Dual Pol. SAR data for snow mapping
AVNIR-2 (06-05-07) Snow Map (ASAR) Snow Map (PALSAR) Snow map (PALSAR)
16. ALOS PALSAR Quad Polarization SLC Data
Snow
Extract Scattering Matrix(S) Detection
Multi-Looked (6×1) in (Azimuth × Range) Algorithm
and make Coherency Matrix (T3) (SDA)
(HV≈VH)
Polarimetric Speckle Filtering
Generate Eigenvalues Image (λ1, λ2, λ3)
Generate Polarization Fraction value image
33
0 PF 1 1
1 2 3
PF >=0.55 && Normalized λ3<0.015 NO
YES Non-snow feasible Area
Snow Area
17. Problem with Single/Dual Pol. SAR Data for Snow Mapping - Resolved by Quad
Pol.
SDA based Snow Map
Snow Cover Area Non-snow
feasible Area
18. snow cover (magenta) derived
from PALSAR (26-05-11),
Discrimination of snow from overlaid to AVNIR-2 (24-05-11)
other Bragg scattering dominant Agassizhorn region,
surface may be problematic. Bernese Alps, Switzerland
L-band fully polarimetric SAR is
not able to detect shallow-depth
snow
19. Study Area
(snow and glacier covered terrain)
Part of Indian Himalaya (place of ice )
Siachen Glacier area Standing snow
Length ~73 km 1.2-8.8 m (low-high altitude)
SWE Product of AMSR-E
Aug., 2007
Feb., 2007
22. [C9] (SHV=SVH) [C5] (SHHS*HV ≈ S VVS*VH ≈0)
SDA
CP [J4] = [Cꞌ5]
(SHHS*HV ≈ S VVS*VH ≈0)
Degree of polarization
[1]-[8] Relative Phase
23. PF-λ3 approach (FP) PF-λ3 approach(FP-RS) PF-λ3 approach (CP) ζ0HV/ζ0HH
22-05-2009 SD126-886 cm (low-high altitude)
Non- snow
m-δ approach
feasible area
FP : Full Polarimetry CP : Compact Polarimetry
FP-RS : Full Polarimetry with Reflection Symmetry condition
Data Dual-Pol CP CP FP-RS FP
Approach σ0HV/σ0HH m-δ PF-λ3 PF-λ3 PF-λ3
Non-snow feasible area 71.38 67.21 56.56 45.52 40.98
(%)
Snow area (%) 28.62 32.79 43.44 54.48 59.02
24. Summary
• Importance of snow studies
• PALSAR backscattering coefficient response for various
features
• Comparisons between single, dual, compact and quad
polarization data for snow detection
• Identification of suitable polarimetric descriptors for
discriminating the snowpack
– PF and normalized λ3
25. Summary
• Results with single polarization SAR (C-&L-band) for snow discrimination
not good.
• Results with dual polarization SAR measurements better than single pol.
But it does not care of unwanted topographic distorted area.
• Full polarimetry SAR technique SDA has produced promising results.
• SDA
……takes care of unwanted topographic distorted area
...... suitable for CP too.
****CP shows capability ̴ 15% less than FP****
