Extraction And Geometrical Structure Retrieval Of Man-made Target In POLSAR Imagery

The extraction and geometrical structure retrieval of man-made target in SAR imagery play important roles in SAR battlefield reconnaissance and intelligence collection applications, and are also advanced issues of SAR image interpretation with much theoretical and applicable significance. To improve the capability of intelligence analysis and processing by POLSAR sensors, the extraction and geometrical structure retrieval of man-made target in POLSAR imagery are investigated in this thesis.Chapter 1 summarizes the current development of typical POLSAR platforms and various techniques of POLSAR image interpretation. The disadvantages of the current research on extraction and geometrical structure retrieval of man-made target in POLSAR imagery are especially analyzed, and the major research topics of this dissertation are also explained.Chapter 2 studies the problem of target contrast enhancement in POLSAR imagery. Traditional enhancement schemes, which select pixel samples with manual intervention, would be of less effect when dealing with regions of heterogeneous polarimetric characteristics. In order to overcome this disadvantage, a novel scheme based on the strategy of sample selection is proposed. The novel scheme, which consists of two sequential sample selection stages, can effectively improve the performance of traditional method. Moreover, a scheme based on the improvement of polarimetirc characteristics similarity is proposed especially for the enhancement of man-made targets in high resolution POLSAR imagery. The enhancement result makes it much easier for the further detection and extraction process. The validities of the two methods proposed in this chapter are indicated by experimental results with fully polarimetric SAR data sets.In Chapter 3, the extraction of man-made target in POLSAR imagery is discussed. Aiming to remedy the deficiency of traditional extraction methods on the integrality and accuracy, novel extraction methods are proposed with more effective features for extraction introduced. By introducing the spectral correlation property, a novel method based on scattering mechanism identification and spectral correlation property analysis is proposed. By introducing the property of polarimetric correlation between like- and cross-polarized channels, another novel method based on scattering mechanism identification and azimuthal symmetry decision is proposed. The two novel methods can accurately extract man-made targets with different polarimetric characteristics, and provide instructive candidates for the construction of multi-features joint man-made target extraction framework. Moreover, the method based on scattering mechanism identification and spectral correlation property analysis has a unique advantage of extracting point-like coherent scatterers and achieving a direct interpretation of these scatterers, which can improve the accuracy of target interpretation.In Chapter 4, the problem of geometrical structure retrieval of man-made target in POLSAR imagery is discussed. Firstly, the space-frequency polarization characteristics of canonical scatterers such as dihedral corner, trihedral corner, plate, are compared, which reveal the potential of space-frequency polarization features to benefit the geometrical structure retrieval of man-made target. A strategy combined with two-dimensional coherent polarization GTD model (2D CP-GTD) and Short-Time Fourier Transform (STFT) is proposed to extract and analyze the spatial polarization characteristics of scattering centers. A novel retrieval scheme based on space-frequency polarization feature is proposed. Compared with traditional retrieval trials, the novel scheme can obtain a more accurate and complete retrieval result by making fully exploitation of the information embedded in space-frequency polarization features, and can offer great benefit to POLSAR image interpretation and automatic target recognition.