Abstract
Abstract. China’s first airborne SAR mapping system (CASMSAR) developed by Chinese Academy of Surveying and Mapping can acquire high-resolution and full polarimetric (HH, HV, VH and VV) Synthetic aperture radar (SAR) data. It has the ability to acquire X-band full polarimetric SAR data at a resolution of 0.5m. However, the existence of speckles which is inherent in SAR imagery affects visual interpretation and image processing badly, and challenges the assumption that conjugate points appear similar to each other in matching processing. In addition, researches show that speckles are multiplicative speckles, and most similarity measures of SAR image matching are sensitive to them. Thus, matching outcomes of SAR images acquired by most similarity measures are not reliable and with bad accuracy. Meanwhile, every polarimetric SAR image has different backscattering information of objects from each other and four polarimetric SAR data contain most basic and a large amount of redundancy information to improve matching. Therefore, we introduced logarithmically transformation and a stereo matching similarity measure into airborne full polarimetric SAR imagery. Firstly, in order to transform the multiplicative speckles into additivity ones and weaken speckles' influence on similarity measure, logarithmically transformation have to be taken to all images. Secondly, to prevent performance degradation of similarity measure caused by speckles, measure must be free or insensitive of additivity speckles. Thus, we introduced a stereo matching similarity measure, called Normalized Cross-Correlation (NCC), into full polarimetric SAR image matching. Thirdly, to take advantage of multi-polarimetric data and preserve the best similarity measure value, four measure values calculated between left and right single polarimetric SAR images are fused as final measure value for matching. The method was tested for matching under CASMSAR data. The results showed that the method delivered an effective performance on experimental imagery and can be used for airborne SAR matching applications.
Highlights
A major research area in Synthetic aperture radar (SAR) image processing is image matching for 3D reconstruction (Toutin, 2000), etc
In order to obtain a more accurate and robust matching points of two overlapping SAR images, we take a special interest to the fullpolarimetric SAR imagery matching method
We use airborne X-band full-polarimetric SAR images obtained by CASMSAR system
Summary
A major research area in SAR image processing is image matching for 3D reconstruction (Toutin, 2000), etc. Area-based image matching methods can provide dense and accurate matching points. They are intolerant to radiometric distortions caused by speckles and imaging geometry (Edwards, 2005). In order to obtain a more accurate and robust matching points of two overlapping SAR images, we take a special interest to the fullpolarimetric SAR imagery matching method. Procedures are described to combine four similarity measures calculated from corresponding logarithmically transformed polarimetric images respectively to ensure that the matching points are determined by all data available.
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