Abstract: A system and a method for determining the correct position for a GPS device from a predefined set of alternatives are provided. Based on the known positions of the visible GPS satellites and of the predefined alternative locations, the system determines theoretical distances between each satellite and each location and/or differences thereof These distances are related to the distance measured between the GPS device antenna and each GPS satellite in order to choose the location from among the predefined location alternatives. Also disclosed are a system and a method for identification of predefined container slots on a freight yard.