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Introduction

 

Polarimetric Backscattering Behavior of River Ice Cover

Stéphane Mermoz(1), Imen Gherboudj(2), Sophie Allain(1), Monique Bernier(3) and Eric Pottier(1)

(1) IETR, 262 avenue Général Leclerc, 35042 Rennes, France
(2) CARTEL, 2500, boulevard de l’Université, J1K2R1 Sherbrooke (QC), Canada
(3) INRS ETE, 490 rue de la Couronne, G1K9A9 Quebec (QC), Canada

Abstract

In many northern rivers of Canada, the formation of the ice covers in cold weather leads to important situations: ice jamming, and then flooding of large areas, reduction of power generation at hydroelectric stations, navigation hindrance and structural damage. In addition, hydroelectric companies and government services require spatially distributed information about the types and characteristics of river ice. So far, the monitoring of the river ice cover has been focused on the use of monopolarized or multipolarized data [1]. With the forthcoming of the polarimetric satellite RADARSAT-2, a series of river ice studies have been undergone to asses the potential information gain from polarimetric SAR data in C-band [2].

The river ice covers can be formed with different ice types such as columnar ice, frazil ice and snow ice. There characteristics (density, thickness, roughness, etc.) can vary horizontally and vertically. In order to understand the interaction of the radar waves with the river ice cover variations, a polarimetric backscattering model is well needed. Gherboudj [3, 4] has studied the modelling of radar backscattering from river ice with the co- and cross-polarization. The used model is based on the Radiative Transfer (RT) theory, which is solved by the Doubling Matrix method [5]. The main parameters of this model are the parameters of the ice matrix that are its thickness, density of each ice type and the size and spatial distribution of air bubbles within it. Based on the physical characterization of the air inclusions within the different ice type [6], the volume scattering of each ice type was modelled using the appropriate theory (Rayleigh, Mie, Dense medium, Rayleigh-Gans). The surface backscattering contribution is modelled using the Integral Equation Method (IEM).

This model is improved to simulate the fully polarimetric response of a river ice cover. The total backscattering information, which is contained into a covariance matrix representation, is investigated. The aim of this paper is to analyse the results of the simulations and to study the relations between polarimetric parameters and river ice characteristics. The final aim of this work is to improve the classification robustness in C-band using RADARSAT-2 data by finding pertinent parameters, and to estimate river ice parameters (thickness, roughness or porosity).

References

1. Gauthier, Y., Weber, F., Savary, S., Jasek, M., Paquet, L.M. and Bernier, M. A combined classification scheme to characterize river ice from SAR data. In EARSeL, eProceedings, vol. 5, no. 1, pp. 77-88, 2006.

2. Mermoz, S., Allain, S., Bernier, M. and Pottier, E. River ice mapping from polsar images. IGARSS08, July 6-11, 2008, Boston, USA. CD-ROM.

3. Gherboudj, I. PhD Dissertation. Institut National de la Recherche Scientifique, Québec, Canada.

4. Gherboudj, I., Bernier, M. and Leconte, R. Understanding the radar interaction with the river ice cover at different polarisations (HH, VV, and VH) and frequencies (C, X, L). IGARSS08, July 6-11, 2008, Boston, USA. CD-ROM.

5. Fung, A.K. Microwave scattering and emission models and their applications. Artech House, 1994.

6. Gherboudj, I., Bernier, M., Hicks, F. and Leconte, R. Physical characterization of air inclusions in river ice. Cold regions science and technology, vol. 49, no. 3, pp. 179-194, 2007.

 

Full paper

 

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