Understanding ERS Coherence over Urban Areas

C-band SAR interferometry has been widely used for several Earth related studies (topography, volcanology, forestry etc.). Nevertheless, not much attention has been paid to urban areas and coherence has been used for classification purposes only. In this study we focused on the meaning of coherence of an urban area and performed several analysis in order to understand what causes decorrelation. Two test sites have been considered: Gothenburg in Sweden and Naples in Italy. For both cities we had a reasonable number of coherence images with one-day and long-period acquisition interval. SAR amplitude images have also been considered. Using RGB colour composite combinations of SAR and InSAR imagery, we could relate the level of coherence of a part of a city either to topography, InSAR system geometry and position of the targets or to image processing or to structural typologies.