Effects of ionospheric constraints in Precise Point Positioning processing of geodetic, low-cost and smartphone GNSS measurements

Abstract

The proliferation of low-cost GNSS hardware smartphones providing multi-constellation, multi-frequency carrier-phase and pseudorange measurements for the Android platform offer an avenue for Precise Point Positioning (PPP) GNSS use in recent years. However, smartphone PPP is restricted due to high multipath effects and signal loss leading to metre-level accuracy and longer convergence time compared against professional-grade GNSS receivers. Proven by previous research, the combination of ionospheric constraints and receiver differential code bias (DCB) estimation is an efficient approach to improve PPP solution initialization. Therefore, this study analyzes the performance improvements by applying ionospheric constraints (IC) to PPP in comparison to conventional PPP solutions for different grades of GNSS receivers (geodetic, low-cost, and smartphone hardware) in open-sky and suburban environments. The results reveal that smartphone PPP enjoys more beneficial effects from ionospheric constraints (IC) than low-cost and geodetic hardware, as a significant 30% improvement in horizontal rms is observed in the first epoch of examined datasets, and a 57% improvement in the first 20 min of data collection. For low-cost and geodetic equipment, the first epoch improvement is only 21% and 18%, respectively. Furthermore, a 44% convergence time reduction for smartphone PPP-IC is observed to attain 1 m level of horizontal accuracy. Based on these investigations, PPP-IC can provide greater impact for those low-quality measurements before convergence, showing potential in achieving fast initialization and accurate positioning within a short time for autonomous vehicles, precision agriculture, and smartphone location-based services.