Position Domain analysis of modernized GPS Ionosphere-free Code Observations

New signals (L2C and L5) are added as a part of GPS modernization to improve the achievable accuracy of the system. Compared to the legacy signals (L1/L2), new signals provide good cross-correlation performance, Forward Error Correction (FEC) and tracking facility. But the systematic errors in range measurements are the concern, particularly due to the ionospheric delay. The ionosphere-free linear combinations of dual frequency code or carrier phase measurements can be used to correct the refraction effects on GPS signals. The availability of L2C and L5 on Block-IIRM satellites has given an opportunity of direct comparison of coded signals instead of carrier-phase measurements. Simulation studies in the open literature on optimal linear combinations are focused in measurement domain. The analysis in respect of precision on coordinate parameters is essential to realize the optimal linear combination in position domain. Two ionosphere-free linear combinations L1/L5 and L2C/L5 of undifferenced/zero-differenced GPS coded signals are investigated for Single Point Positioning (SPP).