Abstract
Abstract. Interferometric synthetic aperture radar (InSAR) has been widely used in remote sensing field, which can reflect actual topographic trend or possible surface deformation. Due to the orbit attitude influence, the flat-earth phase usually causes the interferogram dense and difficult to be used in further procedures. Before phase unwrapping, interferogram must be flattened to derive accurate topographic or deformation information. In this paper, analysis of performance of two methods of flat-earth removal is done. First method uses imaging geometry and second method uses precise orbital information. Further, 3-degree, 5-degree and 7-degree polynomials are fitted in the method using precise orbital information. Validation is done both visually and empirically using entropy as the evaluation index.
Highlights
Interferometric synthetic aperture radar (InSAR) has been an important hotspot and widely used in radar imaging area for its high ability to retrieve digital elevation model (DEM) and surface deformation information, which can reflect such information according to the interferometric phase between two or more images [1]
Sample data is used to validate the two methods described for flat earth removal
In the raw interferogram (Fig. 3), we can clearly see the high frequency parallel fringes, which are a result of flat earth effect
Summary
Interferometric synthetic aperture radar (InSAR) has been an important hotspot and widely used in radar imaging area for its high ability to retrieve digital elevation model (DEM) and surface deformation information, which can reflect such information according to the interferometric phase between two or more images [1]. Phase difference between the scattering elements on the same height level, which is named as flat-earth phase or linear phase, varies because of the spatial geometrical influence and thereby results in the phase offset in the interferogram. This phenomenon is called as flat-earth effect [2]. The phenomenon showed that the interferogram presented periodic interference fringes. These dense parallel stripes observed in an interferogram caused by flat-earth effect can overshadow the phase variety of topographical changes, and bring much burden for subsequent phase filtering and unwrapping. The removal of the flat earth effect is crucial in the InSAR processing [3]
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