DGNSS Corrected Pseudorange and Time-Differenced Carrier Phase (TDCP) Measurements using Differentiable Factor Graph Optimization (DFGO)

Google Smartphone Decimeter Challenge (SDC) provides a dataset for the communities to verify their leading-edge algorithm for precise smartphone GNSS positioning under the same baseline. This year's dataset provides more variety on the vendors of smartphones' GNSS chips, where the new data from affordable smartphones is believed to be noisier, increasing the position uncertainty. This study integrates the pseudorange, time-differenced carrier phase (TDCP) measurements, and estimated velocity using factor graph optimization (FGO) to provide an optimal and robust position estimation. In the optimization process, properly excluding and weighting the measurement is the key for only using healthy measurements for state estimation. This study also uses the differentiable FGO (DFGO) to determine the covariance for the GNSS positioning adaptively. The positioning results show that the network can provide a more robust and reliable performance than the traditional model-based approach.