Comparative study on the speckle filters for the very high-resolution polarimetric synthetic aperture radar imagery

Sheng Sun,Jiayi Ma,Changcai Yang,Ji Zhao,Renfeng Liu,Huabing Zhou

doi:10.1117/1.jrs.10.045014

Abstract

With the emergence of very high-resolution airborne synthetic aperture radar systems, it is necessary to reinvestigate these proposed methods with respect to their despeckling performances. As for the very high resolution polarimetric synthetic aperture radar (PolSAR) data, the presumption that the resolution cell is much larger than the radar wavelength becomes ineffective. Therefore, some classic and new filters are thoroughly reviewed. For the evaluation of speckle filters, both indicators for polarimetric information and spatial information are listed. The absolute relative bias is introduced, with the purpose of measuring the filtering performance concerning the indicators for polarimetric information. Moreover, the ratio of half power point width is employed to quantitatively assess the degree of point target preservation. A series of experiments are carried out based on the real PolSAR imagery which is obtained from an uninhabited aerial vehicle synthetic aperture radar system. It can be concluded that existing filters can only attain good performance with reference to part of the indicators. As regards very high-resolution PolSAR imagery, it is necessary to conceive more apposite new filters or make improved versions of the existing filters.

Highlights

With newly released diversiform missions being finished, the spaceborne and airborne platforms of synthetic aperture radar (SAR) are booming
It is observed that in-depth comparative studies on polarimetric synthetic aperture radar (PolSAR) data are few in number.[1]
Lee et al summarized the speckle filtering principles that are listed as follows: (a) for preserving the statistical characteristics, each term of the covariance matrix should be filtered in a manner similar to multilook processing by averaging the covariance matrices of neighboring pixels. (b) To avoid introducing crosstalk between polarization channels, it was required that each element of the covariance matrix should be filtered statistically independently of other terms. (c) To preserve polarimetric properties, only neighboring pixels with a similar scattering mechanism should be included in the filtering.[5,7]

Summary

Introduction

With newly released diversiform missions being finished, the spaceborne and airborne platforms of synthetic aperture radar (SAR) are booming. As is known to all, speckle filtering is one of the classic topics in the radar remote sensing community. It is observed that in-depth comparative studies on polarimetric synthetic aperture radar (PolSAR) data are few in number.[1] Especially, studies on data of the emerging airborne SAR systems, such as F-SAR,[2] uninhabited aerial vehicle synthetic aperture radar (UAVSAR),[3] and Pi-SAR24 that generally have large dimensions and very high resolution data in single, dual, and quad polarization configurations. Sun et al.: Comparative study on the speckle filters for the very high-resolution polarimetric synthetic. The spatial resolution of these systems is often on a decimeter level and the dimensions are on the order of 10 to 20,000 by 10 to 20,000 pixels.[5] it is necessary to begin an investigation into the filtering performance of speckle filters on very high-resolution PolSAR data

Results

Discussion

Conclusion