Benefit of partial L2C availability to estimate ionospheric delay for dual-frequency GPS ambiguity resolution

This paper evaluates the benefit of the partial availability of GPS satellites with L2C signal capability in estimating the ionospheric delay using the dual-frequency L1/L2 code and phase measurements using real data. Compared to the strategy of estimating one slant ionospheric delay (SID) for each satellite, a simplified single differential zenith ionospheric delay (ZID) method is proposed to account for the ionospheric effect using the limited number of L2C measurements. The algorithms and models are implemented in a Kalman filter (KF) based code and phase observations processor using between receiver single difference (SD) GPS L1/L2 observations. Using data sets from three International GNSS Service (IGS) stations with both L2C and L2P code measurements, the performance of using L1 observations only, L1/L2 dual-frequency observations without estimating ionospheric delay, and L1/L2 dual-frequency observations with estimating either SID or differential ZID is compared in terms of ambiguity resolution (AR) and positioning accuracy in conjunction with ionospheric delay estimation. The results show L1/L2 AR outperforms L1 only in several scenarios, and the proposed method improves vertical accuracy of the fixed position approximately 10 cm with estimating the single differential ZID.