  Mutual usage of vehicles as well as car sharing became more and more
attractive during the last years. Especially in urban environments with limited
parking possibilities and a higher risk for traffic jams, car rentals and
sharing services may save time and money. But when renting a vehicle it could
already be damaged (e.g., scratches or bumps inflicted by a previous user)
without the damage being perceived by the service provider. In order to address
such problems, we present an automated, motion-based system for impact
detection, that facilitates a common smartphone as a sensor platform. The
system is capable of detecting the impact segment and the point of time of an
impact event on a vehicle's surface, as well as its direction of origin. With
this additional specific knowledge, it may be possible to reconstruct the
circumstances of an impact event, e.g., to prove possible innocence of a
service's customer.
