Towards Sub-meter Positioning using Android Raw GNSS Measurements

This paper presents a first analysis on the positioning performance using raw GNSS dual-frequency measurements acquired by the Xiaomi Mi 8 smartphone. In our study, we used the code-only-based Single Point Positioning technique for epoch-by-epoch positioning, and the Precise Point Positioning technique, which is based on both code and carrier-phase measurements, on precise satellite orbit and clock corrections, as well as on a dynamic model to exploit the time-constant property of the phase ambiguities. The functional model used in both our own SPP and PPP algorithms is based on the uncombined GNSS observation equations. As the Xiaomi Mi 8 smartphone is able to track both GPS and Galileo systems in two frequencies, we will present results based on single and combined GNSS solutions in single- and dual-frequency mode. The performance of these solutions will be assessed in terms of their repeatability and accuracy with respect to the ground-truth, while the improvement in Android-based positioning with multiple frequencies and GNSSs will be assessed compared to the GPS L1-only SPP case. An optimal combination of the elevation cut-off angle and the carrier-to-noise density ratio mask will be explored in order to have a reasonable balance between availability and quality of observations. Both real-time and post-processing positioning results will be presented.