# Utilization of Quasi-Zenith Satellite System for Navigation of a Robot Combine Harvester  
[PERSON]  
1 Graduate School of Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-Ku, Sapporo, Hokkaido 060-8589, Japan; kannapat, [EMAIL_ADDRESS];p1  
[PERSON]  
2 Research Faculty Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-Ku, Sapporo, Hokkaido 060-8589, Japan; [EMAIL_ADDRESS];p1  
[PERSON]  
3 Department of Biosystems Machinery Engineering, College of Agriculture and Life Science, Chungman National University, 200 Gun-Dong, Yusung-Gu, Daejeon 305-764, Korea; [EMAIL_ADDRESS]  
[PERSON]  
2 Research Faculty Agriculture, Hokkaido University, Kita-9, Nishi-9, Kita-Ku, Sapporo, Hokkaido 060-8589, Japan; [EMAIL_ADDRESS];p1  
Footnote 1: [[https://www.mdpi.com/journal/agronomy/10/330/](https://www.mdpi.com/journal/agronomy/10/330/)]([https://www.mdpi.com/journal/agronomy/10/330/](https://www.mdpi.com/journal/agronomy/10/330/))  
Footnote 2: [[https://www.mdpi.com/journals/](https://www.mdpi.com/journals/)]([https://www.mdpi.com/journals/](https://www.mdpi.com/journals/))  
Satellite System (GNSS) receiver with a positioning augmentation system. The performance of GNSSs are related to the number of visible satellites, the oscillation of satellite orbits, the satellite clock accuracy, and ionospheric activities [4]. The positioning accuracy could be increased in real time by using the GNSS receiver near a reference or within a reference station's network, which can broadcast the augmentation signal to the receiver. Several researches [5] have addressed the importance of the performance of GNSSs. For example, [6; 7] studied the RTK GNSS technique, the multiple reference stations (MRS), and the virtual reference station (VRS) to increase the positioning accuracy in real time. However, these solutions require a high density of reference stations; therefore, the user of the GNSS receiver needs to be close to a reference station or within the area of a reference station's network. Other related works [8; 9] have studied a technique called the precise point positioning (PPP) which uses the precise orbit and clock of the GNSS for accurate calculation of the user's position. Therefore, this technique does not require a high density of reference stations; but one of the drawbacks of this technique is the limitation of the convergence time and an ambiguous resolution. A similar approach [10] studied a PPP-RTK technique which improves the performance of PPP in terms of the accuracy and the convergence time. Although several researches have addressed the importance of the performance and accessibility of GNSSs, there is too few information reporting the performance of GNSSs, particularly applied to an agricultural robot.  
The performance evaluation of different GNSSs based on factors like the oscillation of satellite orbits and the satellite clock accuracy might be complex and require specialized tools, but it is possible to evaluate their practical application for the positioning of an agricultural robot, such as robot combine harvesters which require both high accuracy and accessibility for the harvesting work.  
Therefore, the purpose of this study is to evaluate the performance of a robot combine harvester using two recently released positioning augmentation systems: the Centimeter Level Augmentation Service (CLAS) and the Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis (MADOCA), both from the Quasi-Zenith Satellite System (QZSS). The QZSS is a Japanese satellite positioning system composed mainly of satellites in quasi-zenith orbits (QZO). Both CLAS and MADOCA use satellite signals from QZSS to obtain position information. Unlike the American Global Positioning System (GPS) whose orbit covers around the earth, the QZO coverage area around Japan and Oceania focuses on its usage in Japan. Therefore, the QZSS is sometimes called the \"Japanese-GPS\"  
The evaluation in this research was divided in two sections; evaluation under static conditions and performance evaluation of a robot combine harvester.