Assessment of QZSS L1-SAIF for 3D map-based pedestrian positioning method in an urban environment

Today, smart mobiles play an important role in our daily life. Most of these devices are equipped with a low-cost GNSS navigation chip. The current low-cost GNSS receiver cannot calculated satisfactory positioning results in urban area with dense building due to the multipath and NLOS effect. This paper develops a rectified positioning method using a basic 3D map and ray-tracing algorithm to mitigate the signal reflection effects. This 3D map method is achieved by implementing particle filter to distribute possible position candidates. The likelihood of each candidate is evaluated based on the similarity between the pseudorange measurement and simulated pseudorange of the candidate. Finally, the expectation of all the candidates is the rectified positioning of the proposed 3D map method. The Japanese QZSS provides two benefits: 1) signal from high elevation and 2) Ll-SAIF correction message. Both advantages can improve the quality of simulated pseudorange for the proposed 3D map method. According to the experiment result, the mean of the positioning error of the 3D map method (using u-blox M8 series commercial receiver) can be decreased from 12 to 6.5 meters by applying QZSS signal. The proposed method will serve as one sensor of integrated system in the future. In this case, the positioning accuracy is required to provide to the integrated system. This paper successfully defines a positioning accuracy, which follow the idea of conventional GPS positioning method, i.e., accuracy = DOP × UERE. The calculated positioning accuracy can capture the trend of the positioning error of the 3D map method in the most of the time.