Tham khảo tài liệu 'geoscience and remote sensing, new achievements part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Methods and performances for multi-pass SAR Interferometry 343 solutions of practical use in InSAR applications. These solutions provide a quick performance assessment of an InSAR system as a function of its configuration wavelength resolution SNR the intrinsic scene decorrelation and the APS variance. Although some limitations may arise at higher wavelengths due to phase wrapping the result may still be useful for the design and tuning of the overall system. 5. Phase Linking The scope of this section is to introduce an algorithm to estimate the set of the interferometric phases pn comprehensive of the APS contribution. As discussed in previous chapter assuming such model is equivalent to retaining phase triangularity namely tynm cpn tym. In other words we are forcing the problem to be structured in such a way as to explain the phases of the data covariance matrix simply through N 1 real numbers instead than N N 1 2. For this reason the estimated phases will be referred to as Linked Phases meaning that these terms are the result of the joint processing of all the N N 1 2 interferograms. Accordingly the algorithm to be described in this section will be referred to as Phase Linking PL . An overview of the algorithm is given in the block diagram of Fig. 4. The algorithm is made of two steps the first is the phase linking where the set of N linked phases are optimally estimated by exploiting the N N 1 2 interferograms. These phases corresponds to the optical path hence at a second step the APS the DEM the target heights and the deformation parameters are retrieved. N-1 estimated phases N images ML estimate linking of Nx N-1 interferograms N-1 estimated phases Standard PS-like processor exp M exp M _exp i _ Fig. 4. Block diagram of the two step algorithm for estimating topography and subsidences. Before going into details it is important to note that phase triangularity is automatically satisfied if the data covariance matrix is estimated through a single sample of the
