Effect analysis of higher-order ionospheric corrections on quad-constellation GNSS PPP

Abstract

With the development of global navigation satellite system (GNSS) precise point positioning (PPP) technology, higher positioning accuracy is required in some applications. An important error source in PPP is the residual higher-order (i.e. second- and third-order) ionospheric error after the first-order ionospheric error has been removed by dual-frequency observation combinations. Generally, higher-order ionospheric errors are negligible; but at high ionospheric activities, higher-order ionospheric errors can reach a few centimeters, which must be considered in high-precision positioning. In this study, a quad-constellation PPP approach with higher-order ionospheric corrections is proposed. The temporal variations of the higher-order ionospheric errors for GPS, GLONASS, BDS and Galileo are analyzed and their effects on quad-constellation PPP are evaluated. The GNSS observations collected at different solar activities are used to analyze the effect of the higher-order ionospheric errors and the results indicate that their magnitudes can reach almost 2 cm for their first frequency signals at high solar activity. The occurrence of geomagnetic storms further increases the higher-order ionospheric errors by a few millimeters. Multi-GNSS datasets collected at low, middle and high latitude stations at different ionospheric activities are processed and the results indicate that the higher-order ionospheric delay can affect the 3D position solutions of the quad-constellation PPP at a maximum of 6 mm.