Ionosphere Sensing With a Low-Cost, Single-Frequency, Multi-GNSS Receiver

The global navigation satellite system (GNSS) data are beneficial for sensing the earth's ionosphere by virtue of their temporal continuity and spatial coverage. In recent years, GNSS (GPS, GLONASS, BDS, and GALILEO) has developed rapidly, with BDS and GALILEO offering position, navigation, and timing services and the ongoing modernization of GPS and GLONASS. The customary approach to sensing the ionosphere normally uses the dual-or multifrequency (DF) data provided by geodetic-grade receivers and consists of two sequential steps. The first step is retrieving ionospheric observables using the carrier-to-code leveling technique. In the second step, using the thin-layer ionospheric model, one can isolate the main vertical total electron content (VTEC) for ionosphere sensing as well as the by-product of the satellite differential code biases (SDCBs) and the receiver differential code biases. In this paper, we proposed a multi-GNSS single-frequency (SF) precise point positioning approach enabling the simultaneous retrieval of VTEC and SDCBs with low-cost receivers. The root mean square of the VTEC differences between the values retrieved from the multi-GNSS SF method and DF method is approximately 0.5 total electron content unit in each system.