Analysis of parked vehicles on very high resolution interferometric images

For several years ONERA has been developing very high resolution (VHR), sub-metric to decimetric range, capabilities in airborne SAR imagery first using the RAMSES system [1], and now the SETHI system [2]. Thanks to a precise trajectory monitoring, it is in fact possible to achieve the challenging task of multi pass VHR interferograms acquisition. In this paper we present the promising potentiality of this mode through the example of parking lots occupancy monitoring. We describe an experiment in which four SAR images were acquired with three cars placed at different locations on an open area. Four parking positions were marked on the ground and some of the vehicles were moved from one location to another between the acquisitions. We show that a colour composite display can differentiate cars parked only during the first flight from those parked only during the second flight; cars which didn't move between the two acquisitions as well as cars which were replaced between the flights. Furthermore, it is shown that, as suggested by theory, a car which is slightly moved between two acquisitions can be distinguished from the other cars by considering its interferometric phase signature. Finally we study the potentiality of interferometry to identify a car that has been moved in the azimuth direction.