Leveraging Ground- and Space-Based GNSS Observations in Precise DCBs and TEC Determination

The combination of ground- and space-based Global Positioning System (GPS) observations was utilized to resolve precise total electron content (TEC) variations. The results show that GPS satellite Differential Code Biases (DCBs) derived from a combination of single ground-based and single space-based observations exhibited significantly greater stability than those calculated using the data from a single station alone, even comparable to the International GNSS Services (IGS) products obtained from 300-station observations during 2019. Furthermore, the stability of GPS DCBs improved as more Low Earth Orbit (LEO) satellite data was used. After removing DCBs, the absolute vertical TEC showed minimal differences between zero- or short-baseline observations, and the differences were less than 3.0 TECU for ground stations and 1.0 TECU for LEO satellites during 2019, respectively. The coordinates of the stations or LEO satellites as well as the distances between two stations or LEO satellites within one group, did not greatly influence the vertical TEC bias between zero- or short-baseline observations during 2019.