MONITORING URBAN DEVELOPMENT USING ENVISAT ASAR

To monitor and manage urban areas a lot of information is necessary for different tasks. One way to obtain such information is to apply change detection to satellite images. A system is developed to apply this technique on SAR images. The core of the system is an adaptive speckle-noise filter. To study urban monitoring it was applied to Envisat ASAR images of Leidsche Rijn, one of the largest housing and industrial developments in The Netherlands at this moment. Special about Envisat ASAR is that it enables to study alternating polarisations. In case of urban monitoring there is evidence that HH and HV are most favourable. Applying the change detection system to these images, both polarisations show different parts of the developments and complete each other. The filter is able to deal with the speckle noise in both polarisations and the increased thermal signal-to-noise level in HV. The major changes that were detected in the Envisat ASAR images corre-spond with the major housing and industrial developments at that moment. Smaller changes corre-spond to smaller developments and relocated objects such as ships. Generally can be said that some changes are better detected in HH and some in HV because of the different scatter mecha-nisms of the developments and their backgrounds, and consequently the ratio between their radar returns. In false alarm reduction one has to be careful not to reject too much true changes. Rejec-tion of false alarms can be done using object-based and context-based features