Estimating and assessing Galileo navigation system satellite and receiver differential code biases using the ionospheric parameter and differential code bias joint estimation approach with multi‐GNSS observations

With the increased number of Galileo navigation satellites joining the Global Navigation Satellite Systems (GNSS) service, there is a strong need for estimating their differential code biases (DCBs) for high‐precision GNSS applications. There have been studies for estimating DCBs based on an external global ionospheric model (GIM) proposed by Montenbruck et al. (2014). In this study, we take a different approach by joining the construction of a GIM and estimating DCB together with multi‐GNSS observations, including GPS, the BeiDou navigation system, and the Galileo navigation system (GAL). This approach takes full advantage of the collective strength of the individual systems while maintaining high solution consistency. Daily GAL DCBs were estimated simultaneously with ionospheric model parameters from 3 months' multi‐GNSS observations. The stability of the resulting GAL DCB estimates was analyzed in detail. It was found that the standard deviations (STDs) of all satellite DCBs were less than 0.17 ns. For GAL receivers, the STDs were greater than for the satellites, with most values