Precise Position Estimation Using Smartphone Raw GNSS Data Based on Two-Step Optimization

Abstract

This paper presents a high-precision positioning method using raw global navigation satellite system (GNSS) observations from smartphones in the Google smartphone decimeter challenge (GSDC). Compared to commercial GNSS receivers, smartphone GNSS observations are noisy owing to antenna limitations, making it difficult to apply conventional high-precision positioning methods. In addition, it is important to exclude outliers in GSDC because GSDC includes data in environments where GNSS is shielded, such as tunnels and elevated structures. Therefore, this study proposes a smartphone positioning method based on a two-step optimization method, using factor graph optimization (FGO). Here, the velocity and position optimization process are separated and the velocity is first estimated from Doppler observations. Then, the outliers of the velocity estimated by FGO are excluded, while the missing velocity is interpolated. In the next position-optimization step, the velocity estimated in the previous step is adopted as a loose state-to-state constraint and the position is estimated using the time-differenced carrier phase (TDCP), which is more accurate than Doppler, but less available. The final horizontal positioning accuracy was 1.229 m, which was the first place, thus demonstrating the effectiveness of the proposed method.

An open-source software package for Precise Point Positioning: raPPPid

“…Since the release of Android 7.0 in 2016, Android users have had access to the raw GNSS measurements of their smartphones (Zangenehnejad and Gao 2021). Therefore, it is possible to use self-developed positioning algorithms to calculate the smartphone position (Shinghal and Bisnath 2021; Wang et al 2021;Suzuki 2023). However, smartphones are equipped with simple, cost-effective chips and antennas, typically providing low-quality single-frequency measurements and various challenges (Zhang et al 2018;Liu et al 2019;Wanninger and Heßelbarth 2020).…”

Comprehensive Analysis of Xiaomi Mi 8 GNSS Antenna Performance

“…For example, DGPS eliminates specific errors, including atmospheric There are several challenges associated with smartphone positioning in contrast to commercial GNSS receivers, which primarily rely on antennas and exhibit inferior performance and higher levels of noise in observational data compared with positioning using a commercial GNSS receiver [9]; the exhibited lower performance and high noise level in observation data are mainly due to the antenna. The usual positioning accuracy of a smartphone is approximately 3-10 m, which results in significant challenges in applying conventional high-precision positioning methods such as PPP and RTK [10]. Each general antenna must meet the requirements of its intended application and be designed to evaluate parameters and characteristics to assess the performance of an antenna and ensure reliable and effective operation in real-world scenarios.…”

Breaking the One-Meter Accuracy Level with Smartphone GNSS Data

“…Before Android 7.0 was officially released in 2016, it was only possible to read out the position solution of a smartphone's internal algorithm [1,2]. Nowadays, everyone can access raw GNSS measurements tracked by Android smartphones and directly use the smartphone's GNSS observations to estimate the user's position [3][4][5]. Therefore, developing specialized algorithms and applying correction data can enhance positioning performance.…”