Navigation of a Robot Tractor Using the Japanese Quasi-Zenith Satellite System (Part 1)

—Application of Precise Point Positioning Method to a Robot Tractor—

Abstract

We have applied PPP (Precise Point Positioning) using the LEX (L-band Experiment) signal of the QZSS (Quasi-Zenith Satellite System) to a robot tractor for precise farming. The QZSS transmits augmentation signals coded in the LEX signal to realize centimeter-class positioning accuracy. The usage of PPP in autonomous navigation is restricted in ambiguity resolution. Experiments using a commercial QZSS receiver reveal that the PPP converges to different results at the same position, and the results drift after convergence. We proposed a bias identification method based on landmarks to overcome these limitations. The proposed method was effective for navigating a robot tractor with 5 cm accuracy at a speed of 3.6 km/h.