Synthetic Aperture Radar Interferometry Figure Phase Filtering Method

Synthetic Aperture Radar (SAR) is a new Radar system technique which can acquire signal from the earth surface and form images with very high resolution. It has been widely used on military and commercial aspects. SAR can not be disturbed by weather and also the signal can penetrate clouds and forests. In addition, longer wavelength has the ability of penetrating some particular materials underground and therefore can be used to do underground detection/observation. Interferometric SAR (InSAR) is one of the most important developments of SAR technique. It can be used to generate Digital Elevation Model (DEM) From 70's in last century, InSAR technique has been being developed rapidly not only in theory but also in practice. In terms of its applications, there are lots of significant achievements in topographic surveying, earthquake monitoring, volcano monitoring, deformation detection, etc.In InSAR process, the most important step in the chain process is phase unwrapping, Its quality is controlled directly by the quality of the interferogram. Because of the spatial decorrelation, which is the baseline between the two satellites, and the temporal decorrelation, which is the time difference between the two acquisitions, lots of noise occurs in the interferometric phase images. Other noise, such as thermal noise, also exists in the interferogram. The interferometric phase images must be filtered before phase unwrapping to improve the accuracy of DEM. The main work and innovations of this thesis are list as follows:1,The creating process of interferogram was introduced, the characteristic of interferogram stripe and the origin of phase noise were analyzed.2,The phase filtering algorithms was sorted, the more famous filter phase algorithm was analyzed and derived, a program to implement these algorithms was made.3,On the base of the traditional spatial filtering, This paper propose a new phase noises reduction method based on selective keep edge for phase noises reduction with variance as even estimate of each neighborhood, filter processing have been conducted in the complex plane. The new method not only makes the best maintenance to the fringe's texture while at the same time filter out the noises, but also obtains good visual effect of filtered interferogram.4,In allusion to the unilateralism of evaluation methods, This paper propose a new evaluation method , method of synthetically evaluating, which has been used to evaluate the windage degree of the filtering phases.5,In order to evaluate effects of different filtering algorithms, both simulated and real data has been used to evaluate the performance of the filtering techniques qualitatively and quantificationally, Mean, Square, Residue number, edge-holding index, method of synthetically evaluating those are also used to verify the feasibility and validity of the new algorithm.