GPS precise positioning with pseudorange evaluation using 3-dimensional maps

The accurate and reliable positions of pedestrians are important and useful information. Although global positioning systems (GPSs) in smartphones are currently the most convenient devices to obtain the positions of pedestrians, GPSs still have problems with their accuracy and reliability because of the performance degradation caused by multipath and non-line-of-sight (NLOS) propagation in urban canyons. This study describes an approach to estimate a position by searching around the reference position. Position candidates are prepared and evaluated based on the similarity between the simulated pseudorange from the candidate and the observed pseudorange. Simulated pseudoranges are calculated on the basis of a ray-tracing simulation. The proposed method was verified through field experiments in urban canyons in Tokyo. It successfully estimates the reflection paths and direct paths so that the estimate appears very close to the ground truth even though the GPS result is far away from the ground truth.