Sensitivity of Receiver Differential Code Bias Estimates to Mapping Functions

Accurate estimations of differential code biases (DCBs) are critical for producing absolute ionospheric measurements using global navigation satellite system observables. DCB estimation generally requires translating slant total electronic content (TEC) measurements to the vertical domain using a mapping function. Analyzing DCB estimates from regional modeling and global ionospheric maps (GIMs) over 4.5 years reveals significant DCB differences across different mapping functions, varying by a few nanoseconds. Decompositions of receiver DCB estimates show that for some mapping functions, such as the Jet Propulsion Lab extended slab function and the 350-km thin shell function, variations in DCB estimate over time can be largely accounted for by temperature and ionospheric activity. In contrast, other mapping functions, such as the 450-km thin shell function, exhibit significantly less variation over time. Our computational and analytical results suggest the importance of selecting an appropriate mapping function for accurate DCB and TEC estimation from GIMs and shell-based spatiotemporal models.