Combining a differential global positioning system and double electric compass to improve multi-path error correction for a high-precision agricultural robotic vehicle

This work has addressed the improving of the multi-path error in positioning systems by coupling a differential global positioning system (DGPS) and double electric compass (DEC) in the navigation system of an orchard robotic vehicle. A novel corrective algorithm model was applied to predicting the positioning coordinates during vehicle movement. The model manipulates a combination of data from both the DEC and the DGPS when the DGPS receiver is in problematic conditions in which the horizontal dilution of precision (HDOP) is higher than three and the number of satellites is fewer than six. The constructed corrective algorithm model, the DEC and the DGPS together form a combined DGPS-DEC system that is inexpensive and of high-precision fitting for a vehicle-guiding instrument. In a field test in an outdoor environment with sections of tree shade in the guiding path, the combined DGPS-DEC positioning system effectively improved the reliability of positioning by correcting the DGPS multi-path error precisely to within 20 cm. By applying a mini-sprayer, further agricultural applications were feasible. In summary, the combined DGPS-DEC positioning system can obtain the correct position of a vehicle in real time for agricultural applications