Improving GPS positioning precision by using optical encoders

A real-time positioning system for a precision chemical applicator has been developed; the system is composed of a low cost GPS combined with two optical encoders. GPS has good resolution in global range, but has poor resolution in local single-point positioning. With the optical encoders, the situation is just the opposite-they have high resolution in a small range, but the accumulative error grows as the vehicle moves. Based on the characteristics of GPS and optical encoders, an algorithm has been proposed to integrate the advantages of GPS and optical encoders. The results of this research show that the combined positioning system of GPS and the optical encoders can inherit all advantages of GPS and optical encoders and overcome their shortcomings. The positioning accuracy has been significantly improved, and can meet the real-time spatial high resolution positioning demands in field operations with the dynamic response of optical encoders.