A grid-based transmission system for determining relative positions of vehicles in a grid quadrangle of a reference grid, each vehicle having a transmitter and a receiver, comprising determining an absolute position of a vehicle. A reference grid is obtained. A reference point for the reference grid is assigned; and a relative position of the vehicle relative to the reference point is generated. The reference grid is a stored and previously generated reference grid, or is generated based on the absolute position and a transmission range of a transmitter. The vehicle sends a position message containing the relative position; the transmission range; an identity of the vehicle; an identity for all other vehicles that have previously sent a position message received by the vehicle; and the relative position of the all other vehicles.