Assessment of Alternative Positioning Solution Architectures for Dual Frequency Multi-Constellation GNSS/SBAS

Modernized multi-frequency, multi-constellation GNSS will enable higher availability in precision approach procedures to be obtained and reduce requirements for augmentation infrastructure. Three architectural areas are considered in this paper. First, alternative carrier smoothing architectures are proposed and analyzed; a modification of the standard ionospheric-free approach may offer some advantages. Next, a reexamination of tropospheric delay error modeling shows that cross correlation terms that have been ignored lead to errors in vertical protection levels which potentially could lead to hazardously misleading information. Finally, an initial assessment is provided on the utility of precision time aiding for aircraft precision approach availability. The availability enhancement suggests that continued development of clock aiding technology for aviation applications is warranted.