slide 22

SAR image data is called backscatter. After processing, it becomes single loop complex (SLC) data expressed by complex values. Complex values show phase angle and signal amplitude. Phase angle is the angle from the original phase cycle and amplitude is the length of the complex value. SAR data has two applications: SAR application focuses on analyzing backscatter amplitude for surface characteristics, while in-SAR application uses interference between two SAR images to estimate object elevation and displacement. The data in SAR image is called backscatter. After implementing range compression and Doppler beam sharpening, the data is called single loop complex, SLC. It is expressed by a complex value. The reason for using the complex value is that the complex value can show the angle of the phase and the amplitude of the signal. The angle of the phase means the angle from the original phase cycle. We can see the figure. The amplitude is the length of the complex value. The phase is the angle starting from the real axis. We can obtain the amplitude of the signal by the square root of the squared S plus squared Y. The angle of the phase is calculated by octanger. In general, the applications of SAR data are categorized into two groups. One is SAR application and another is interferometry SAR, in-SAR application. SAR application focuses on the analysis of the amplitude of the backscatter. The amplitude is converted to intensity and then converted to radar cross section. Because the amplitude is determined by the surface properties, such as roughness, geometry, and dielectric constant, we can use the amplitude to monitor the surface characteristics. In-SAR application focuses on the phase information. The phase in the backscatter is the distance between target and object on the ground. But in-SAR application doesn't use the phase in one SAR data because we cannot obtain useful information from one SAR image. Instead, it does interference between two SAR images. And it is able to estimate the elevation of the object on the ground and the displacement between two SAR acquisition types. I will first talk about the concepts relevant to SAR application and then talk about in-SAR later.