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INFLUENCE OF SPECKLE FILTERING OF POLARIMETRIC SAR DATA ON DIFFERENT CLASSIFICATION METHODS. Fang Cao 1 , Charles-Alban Deledalle 1 , Jean-Marie Nicolas 1 , Florence Tupin 1 , Loïc Denis 2 , Laurent Ferro-Famil 3 , Eric Pottier 3 , Carlos López-Martínez 4
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INFLUENCE OF SPECKLE FILTERING OF POLARIMETRIC SAR DATA ON DIFFERENTCLASSIFICATION METHODS Fang Cao1, Charles-Alban Deledalle1, Jean-Marie Nicolas1, Florence Tupin1, Loïc Denis2, Laurent Ferro-Famil3, Eric Pottier3, Carlos López-Martínez4 1 Institut Télécom, Télécom ParisTech, France 2 Université de Lyon, France 3 Université de Rennes 1, France 4 Universitat Politècnica de Catalunya, Spain Tuesday, 26/07/2011, Vancouver, Canada, IGARSS 2011
Index Index Introduction Speckle filtering Decomposition and classification Conclusion page 2
Introduction Introduction • Speckle filtering: • A pre-processing step to reduce the speckle noise before image segmentation or classification Tested filters: Refined Lee’s filter, IDAN filter and NL-PolSAR filter • Decomposition and classification: • Evaluation of the performance of speckle filtering methods through Cloude–Pottier decomposition and Wishart H/alpha classification page 3
Index Index Introduction Speckle filtering Decomposition and classification Conclusion page 4
Speckle filtering approaches page 5
Speckle filtering approaches page 6
Speckle filtering approaches page 7
Speckle filtering approaches page 8
Speckle filtering approaches page 9
Speckle filtering approaches Refined Lee IDAN NL-PolSAR |SHH- SVV| |SHV| |SHH+ SVV| San Francisco (JPL L-Band AIRSAR)
Speckle filtering approaches Refined Lee IDAN NL-PolSAR |SHH- SVV| |SHV| |SHH+ SVV| Flevoland (JPL L-Band AIRSAR)
Index Index Introduction Speckle filtering Decomposition and classification Conclusion page 12
Cloude-Pottier Decomposition • Eigenvalue/eigenvector calculation of the coherency matrix of fully polarimetric SAR data. • Covering the whole range of scattering mechanisms • Automatically basis invariant. Coherency matrix: Hermitian, semi-definite positive matrix → diagonalization
Cloude-Pottier Decomposition Probability of each 3 scattering mechanism Entropy H: the global distribution of scattering mechanism angle: the type of scattering mechanism Anisotropy A : the two least important scattering mechanism effects
1.0 0 b Entropy Alpha Anisotropy 90° 0 1.0 0 Refined Lee IDAN NL-PolSAR San Francisco by JPL L–Band AIRSAR
1.0 0 b Entropy Alpha Anisotropy 90° 0 The refined Lee filter and the NLPolSAR filters have similar performance. The IDAN filter usually introduces bias in entropy and anisotropy values, which may result to unreliable classification results. 1.0 0 Refined Lee IDAN NL-PolSAR San Francisco by JPL L–Band AIRSAR
The Wishart H Classification Building Forest Water H/ initialization: 8 classes
The Wishart H / Classification Wishart clustering • Supervised algorithm • Based on the complex Wishart distribution of coherency matrix • Use maximum likelihood criterion Distance measure V : the cluster center coherency matrix : the trace of a matrix Maximum likelihood criterion
Decomposition and classification Refined LEE NL-PolSAR AIRSAR ALOS/PALSAR Radarsat–2 page 19
Decomposition and classification Refined LEE The results of AIRSAR, ALOS/PALSAR and RadarSat-2 data show that the classification results with different sensors are quite similar, except the water area in the AIRSAR data, which is due to the big variation of the incidence angle of the airborne sensor. NL-PolSAR AIRSAR ALOS/PALSAR Radarsat–2 page 20
The NL-PolSAR filter has better performance than the refined Lee filter, for example, the golf course areas and the lakes in the AIRSAR classification results.
Index Index Introduction Speckle filtering Decomposition and classification Conclusion page 22
Conclusion • Comparison of 3 speckle filters: Refined Lee’s filter, IDAN filter and the NL-PolSAR filter • Comparison of the influence on decomposition and classification Cloude-Pottier decomposition & Wishart H/a classification • Obtained results with different sensors: Radarsat-2, ALOS/PALSAR and AIRSAR • The NL-PolSAR filter achieves the best performance in our experimental tests
Thank you! page 24