Author:

Keywords:

PS-InSAR, change detection, monitoring cultural heritage, Cairo

Abstract:

Monitoring urban changes is very relevant, particularly when the cultural heritage is involved and can be affected for its environment. The urban sprawl of Cairo and its surroundings in the recent years is rapidly encroaching the Pyramid area in Giza, and this activity have to be analyzed carefully. This paper investigates the potential of time series analysis of SAR data for extracting 3D information within the city of Cairo and its surroundings using a persistent scatter approach. This technique allows to obtain height information for the most stable points (persistent scatters) along the period of study. For this analysis, more than fifty Envisat SAR images over the city of Cairo covering the period from 2004 to 2010 were used. The images were first processed with the InSAR processor from the Delft University of Technology, named Doris (Delft object-oriented radar interferometric software). This software package is crucial for the coregistration and resampling of the original data and generation of all the interferograms. After selecting the most suitable images by setting the maximum perpendicular baseline between interferogram pairs to 700 meters, persistent scatter processing was done using the Delft PSI (DePSI) package. This tool uses amplitude dispersion for selecting the persistent scatters, i.e. the points that show a stable behavior through time. DePSI also applies atmospheric correction and noise filtering. This processing chain is applied three times: first to the whole dataset (2004-2010) and then subsequently to the data covering the period from January 2004 till August 2006 and from September 2006 till December 2010. Moreover, change detection was applied to obtain quantitative information on the 2D evolution of the city. Combining both PS-InSAR and change detection results it is possible,on one hand to obtain height information of the stable points and on the other hand, to interpret the causes of this changes of the areas where it was not possible to get height information of the whole period under study. Changes in the 2D and 3D urban environment are also investigated on a more detailed scale, i.e. the Giza district. As a result, a persistent (non-changing) 3D profile of the city is constructed for each period. Combining this information with a change detection analysis, provides a quantitative view on areas experiencing an important 3D change in the period under study, As such it enables to investigate the 3D evolution of the city of Cairo and its surroundings.