Evaluation of the damages provoked by seismic events through teledecteted imagery

The availability of high resolution satellite stereopairs also for the civil users opens new possible fields of application among which the automatic extraction of digital models of the surface, the stereoscopic restitution, as well as the possibility to appraise changes and transformations of areas following catastrophic events, as for instance seismic events. In this last case, obviously, as for all the monitoring studies, it is necessary to effect a comparison with the situation before the event. Photogrammetry can fortunately also use older aerial acquisitions, very useful when substantial changes have occurred in the territory; normally, such historical aerial frames are easily available at a very reasonable cost. In this paper is illustrated an experimentation including a first series of tests to evaluate the real possibilities of use of high resolution satellite images, acquired by the Ikonos satellite, to estimate changes caused by a seismic event happened in September 1997 in central Italy, causing relevant damages to a lot of buildings in the zone. It is interesting to evaluate the different capabilities of change detection tecniques on single images and the difference of DSMs extracted by aerial and satellite stereopairs. As reference have been assumed ortophoto maps and aerial frames of the same zone, acquired in years antecedent to the seismic event. From the comparisons, it is possible to underline the variations in the urban areas as the presence of new constructions, changes of the roads, areas with different use of the ground, etc.