Method for determining a position of a trailer attached to a vehicle relative to the vehicle and driver assistance system for a vehicle

The method involves detecting an area formed at opposite longitudinal sides of a trailer (3) using detector devices (10) that are arranged at opposite longitudinal sides (4) of a vehicle (2). Tilting of the trailer around a longitudinal axis is determined for determining a position of the trailer relative to the vehicle. The detector devices are calibrated based on a reference-target pattern. Warning is provided to a driver during over-exceeding a threshold of tilting. Air pressure loss in a tire (16) of the trailer is determined based on the determination of tilting. An independent claim is also included for a driver-assisting system for determining position of the trailer relative to the vehicle.