Monitoring Building Stability in Port-Said City, Egypt Using Differential SAR Interferometry

Abstract

Monitoring the buildings and ground deformations caused by natural or various anthropogenic activitiesare a key requirement in order to prevent damages to structures and utilities at the ground surface. Inrecent years the differential interferometric Synthetic Aperture Radar (DInSAR) technique hasdemonstrated its potential as a land and a building deformation measurement tool. Its capability has beenconsiderably improved by using multiple SAR images acquired over the same area at different times.With these advances the DInSAR technique is becoming increasingly a very reliable quantitative geodetictool for deformation monitoring, rather than simply a qualitative tool. In this work, eight ALOS/PALSAR(L-band 23 cm) radar scenes covering the period from November 2007 to April 2010 were used tomonitor the building stability in Port-Said City, Egypt. The eight PALSAR scenes were co-registeredusing 125 well distributed ground control points (GCPs) with an RMS error mean of 0.029. The coregisteredeight SAR data were used to generate 22 interferogram pairs and estimate the coherence ofeach pair. These 22 interferograms were filtered and used together with the coherence data to calculatethe phase unwrapping. The 22 3D-phase-unwrapped interferogram-pairs were evaluated to discard theinterferograrms that were affected by phase jumps and ramps. Since our area of interest is an urban area,the high-coherence pixels (~ 0.45 to 8) were selected for estimating the vertical displacement. Finally,both the 3-passes and persistent scatter DInSAR methods were performed to map the land and buildingsubsidence in Port-Said City, Egypt during the investigated period. The total vertical displacement duringthe investigated period was found to be 17mm. Keywords: Radar satellite; phase estimation; land-subsidence; Port-Said; Egypt