GNSSFormer: Enhancing GNSS Single Point Positioning Performance Based on Transformer for Smartphone

The Global Navigation Satellite System (GNSS) provides continuous high-precision positioning, enabling many applications such as vehicle navigation and pedestrian monitoring. However, in challenging environments such as urban canyons, positioning accuracy is significantly degraded due to multi-path and non-line-of-sight (NLOS) issues. To tackle this issue, we introduce a single point positioning (SPP) framework based on pseudorange correction, including three modules: feature extraction, pseudorange correction, and positioning model. Heavy pseudorange error is the primary cause of inaccurate localization, and in particular, we introduce GNSSFormer, a transformer-based model to obtain the pseudorange correction values. After preprocessing raw observations of GNSS, we designed a pseudorange correction model GNSSFormer containing a temporal transformer block and a multi-satellite joint spatial transformer block. GNSSFormer extracts multiple features related to both satellites and receivers, learning the complex global relationships between these features and the pseudorange errors to derive correction values. Subsequently, an extended Kalman filter (EKF)-based rauch tung striebel (RTS) smoothing SPP algorithm is employed to determine the location. Validation demonstrates that GNSSFormer significantly enhances SPP performance compared to state-of-the-art algorithms, improving positioning accuracy at least by 29.42% and 28.40% on two open source datasets and 18.91% on real-world dataset.