Instantaneous Cycle Slip Detection, Code Multipath Mitigation and Improved Ionospheric Correction for Enhanced GPS Single-Frequency Positioning

The inadequate accuracy of the broadcast Klobuchar ionospheric correction model for a single-frequency GPS receiver, the multipath error in the observed code pseudoranges and the cycle slips in the phase observation, are known to limit the positioning accuracy and precision of such a receiver. The accuracy impediment due to ionospheric delay is known to be greater in the equatorial and polar regions where the Klobuchar model is less effective. Moreover, in challenging environments where cycle slips are prevalent, the code pseudorange smoothing that is dependent on continuous phase observation is hindered, and existing code smoothing techniques become limited in performance thereby unable to achieve continuous code smoothing to mitigate the inherent code multipath error. As a solution to these single-frequency positioning challenges, this paper introduces a new method that integrates a new single-frequency instantaneous cycle slip detection and correction (CSDC) algorithm based on Optimum Time Differencing (OTD) of a single-satellite phase-only observation; an improved ionospheric delay correction (IIC) algorithm; and code multipath error mitigation, with a view to enhancing GPS single-frequency positioning even in challenged environments. The performance of this new method has been examined in both static and kinematic domains. The results revealed that the new method achieved, on average, more than 98% detection and 92% correctly fixed cycle slips out of the total number of simulated cycle slips in both domains. The IIC results show the capability of the method in improving the broadcast ionospheric delay correction - significantly in the equatorial region, whilst the positioning results indicate its ability to mitigate code error and the impact of phase cycle slips in code smoothing and subsequently in the point positioning. Compared to the widely used Hatch filter (code smoothing technique), coupled with the broadcast Klobuchar ionospheric correction model, the new method gave better performance: it achieved within 21 - 42% improvement in the positioning accuracy, with the most improvement in the height component (24 - 44%). The CSDC algorithm also enables the estimation of receiver clock jumps.