Interpretation of multi-aspect high-resolution polarimetric SAR images

The aim of this article is to explore new methods to enhance the results of automatic interpretation of SAR images by combining images acquired from different viewing directions (multi-aspect SAR images). Using the combined information extracted from multi-aspect images allows to resolve problems of obscurance, by for instance the borders of a forest, to increase the resolution and to augment the confidence in detection as compared to detection in single images. The article focuses on high-resolution polarimetric images for the automatic interpretation of an airfield scene. Specifically for this type of images we have developed a set of new image interpretation tools such as edge detectors and bar (line) detectors, both based on multi-variate statistics. These detectors are briefly described in the article. The main part of the proposed article will focus on how the use of multi-aspect images can enhance the results of these detectors. The multi-aspect images are supposed to be accurately registered. It is thus possible to warp them into a common coordinate system. Because the spatial resolution of a SAR system is usually not the same in range and azimuth, it is sometimes better to detect objects in each image separately and fuse the results of the detection at the object level. This is particularly true for the detection and delimitation of the buildings. On the other hand, edge detectors can benefit from combined information on a pixel-level. In particular, edge detectors based on multi-variate statistical methods can be applied on registered images, thus increasing the confidence level of detection and reducing the false alarm rate, by combining the information at a low level. For edge detectors we will compare results of combining the information available from multi-aspect polarimetric images at different levels. In particular we will compare the results of applying them directly to the registered image set with these obtained when applying them on each individual image and fusing the results at the object level or intermediate (edge-strength) level. Similar investigations will be presented for the bar detectors. Results will be shown on a set of polarimetric L-band images of an airfield.