Visual interpretation of polarimetric SAR imagery

A study is presented in which several different representations of polarimetric SAR data for visual interpretation are evaluated. Using a group of observers the tasks 'land use classification' and 'object detection' were examined. For the study, polarimetric SAR data were used with a resolution of 3 meters. These data were obtained with the Dutch PHARUS sensor from two test areas in the Netherlands. The land use classes consisted of bare soil, water, grass, urban and forest. The objects were farmhouses. It was found that people are reasonably successful in performing land use classification using SAR data. Multi-polarised data are required, but these data need not to be fully polarimetric, since the best results were obtained with the hh- and hv-polarisation combinations displayed in the red and green colour channels. Detection of objects in SAR imagery by visual inspection is very difficult. Most representations gave minimal results. Only when the hh- and hv-polarisation combinations were displayed in the red and green channels, somewhat better results were obtained. Comparison with an automatic classification procedure showed that land use classification by visual inspection appears to be the more effective. Automatic detection of objects gave better results than by visual inspection, but many 'false' objects were also detected.