A leader location-determining receiver determines a leader location of a lead vehicle. A follower location-determining receiver determines a follower location of a follower vehicle, which has a container for storing a material. A data processor or position module calculates an observed relative position between the lead vehicle and the follower vehicle. Target relative positions are established between the lead vehicle and the follower vehicle. A data processor or selector selects a preferential one of the established target positions. A data processor or adjuster adjusts the observed relative position of the follower vehicle to achieve the selected preferential one of the established target positions.