Visualisation of cross-polarised response patterns over short vegetation

Abstract

The analysis of polarimetric response patterns for earth science applications has been hindered by difficulties in attributing phenomenological response patterns to interactions between polarized waves and multi-layered landscapes, such as forested and agricultural areas. Traditional analysis of response patterns relies on the use of areal responses to characterize landscapes. It is shown in this paper, however, that the variability of response patterns within apparently homogenous areas may provide extra information on the nature of polarimetric interactions. A new technique is described, which allows the synoptic analysis of response patterns over these sub-scenes. Using this technique, it is found that response patterns over forested areas are too variable to provide a basis for classification. However, an area of reed beds within the forest image produces a response pattern that is consistent over large areas. This distinctive pattern is more widespread in the agricultural scene, suggesting that it may be the result of coherent interactions between stalks and the underlying surface. The results of this approach are made more significant by the fact that the characteristic response pattern cannot be achieved by additively combining idealized response patterns, and suggests that the response is caused by coherent effects. As the use of additive modelling is common within polarimetric radar research, it is proposed that further research into the nature of the observed response patterns may provide useful additional information which can be incorporated into future models.