To monitor urban areas using a synthetic aperture radar (SAR) sensor, we propose a symmetric analysis-based building signature extraction method. Instead of using separated algorithms, a unified framework is proposed to extract both layover and shadow areas. Since these two primitives usually exhibit long strip patterns in very-high-resolution SAR images, symmetry axes are first delineated. After that, local features are extracted from both symmetry and range direction to better distinguish different primitives. Then, these local radiometric features are used to identify different categories (layover, shadow, and background) via an efficient multiclass logistic regression classifier. To discriminate individual primitives, geometric information is adopted via an improved Ramer Douglas Peucker algorithm, which also simplifies the parameters for describing these primitives. To further enhance accuracy, combinatory analysis is implemented to exclude some false detections, and then shadow areas are extended via a local region growing method. The proposed approach is tested on a 0.75-m resolution airborne C band SAR image. The experiments are carried out under both small- and large-scale scenes, and the comparative results show our method has some advantages in low-contrast target detection and false-alarm elimination.
Proc. SPIE. 4894, Microwave Remote Sensing of the Atmosphere and Environment III
KEYWORDS: Electronics, Digital signal processing, Real time imaging, Image compression, Doppler effect, Synthetic aperture radar, Image segmentation, Image processing, Signal processing, Parallel computing
Real-time imaging processor can provide Synthetic Aperture Radar (SAR) image in real-time mode, which is necessary for airborne SAR applications such as real-time monitoring and battle reconnaissance. This paper describes the development of high-resolution real-time imaging processor in Institute of Electronic, Chinese Academy of Sciences (IECAS). The processor uses parallel multiple channels to implement large-volume calculation needed for SAR real-time imaging. A sub-aperture method is utilized to divide azimuth Doppler spectrum into two parts, which correspond two looks. With sub-aperture method, high processing efficiency, less range migration effect and reduced memory volume can be achieved. The imaging swath is also divided into two segments, which are processed in a parallel way. Range-Doppler algorithm, which consists of range migration correction and azimuth compression, is implemented in the processor. Elaborate software programming ensures a high efficient utilization of hardware. Experimental simulation and field flight indicate this system is successful. The principles, architecture, hardware implementation of the processor are presented in this paper in details.