Improvements to GNSS-based Ionospheric Monitoring using Low-Elevation Single-Frequency Wideband Signals

Ionospheric monitoring is greatly benefitted by the utilization GNSS observations. GNSS-based estimates of ionospheric total electron content (TEC) are useful for the improvement of satellite navigation systems receiver measurement inaccuracies and for ensuring dependable navigation and positioning capabilities. Additionally, TEC estimation is a valuable measure in the study of space weather. This study investigates an innovative approach to refine TEC estimates by reducing measurement noise and multipath effects by analyzing single-frequency wideband GNSS signals. Traditionally, ionospheric TEC estimation relies on L1 and L2 dual-frequency GNSS pseudorange measurements. The large pseudorange noise associated with L1 and L2 narrowband signals may be smoothed by their corresponding carrier phase estimations. However, multipath effects and carrier cycle slips at low elevations can render the carrier phase measurements unusable. Consequently, many ground-based GNSS monitoring stations restrict measurements from low-elevation satellites. However, these low-elevation signals carry valuable ionospheric information, having traversed longer ionospheric paths.