A GNSS system in combination with a hydraulically-actuated, airborne dispenser for a dry material crop dusting system to optimize the distribution of dry materials over a particular tract of land. A GNSS subsystem is included using at least one GNSS antenna and one GNSS receiver located on the aircraft. The aircraft is equipped with an electronic/hydraulic crop dusting subsystem connected to a GNSS CPU. The GNSS ranging signals received by the antennas are processed by a receiver and processor system for determining the vehicles position and dynamic attitude in three dimensions (3D). The system is adapted for operation in a differential GNSS (DGNSS) mode utilizing a base station at a fixed location.