The Precise Point Positioning (PPP) method can be used to obtain centimeter-level positioning accuracy by employing only one GNSS receiver. Measurement errors are mitigated or removed using error modeling and correction products generated from a network of global reference stations. Local reference networks are not required, providing cost savings.
PPP has been a popular research topic in the last ten years. However, it is still unsuitable for many applications, because of long solution convergence times, un-reliability of ambiguity resolution, difficulties in solution re-convergence and lack of reliable integrity monitoring. This paper summarizes the research efforts carried out in the Innovative Navigation using new GNSS Signals with Hybridized Technologies (iNsight, http://www.insight-gnss.org/) project to address these limitations to the widespread application of PPP
In this paper, four commonly used methods in the literature for PPP narrow-lane ambiguity resolution are compared using real GNSS data: bootstrapping (Laurichesse et al., 2010), integer least-squares using the constant threshold ratio test (Geng et al., 2009), integer least-squares using the ratio test with a fixed confidence level also referred to as the Doubly Non-Central F-distribution (DNCF) based method (Feng et al., 2012) and integer least-squares using the ratio test with a fixed failure rate (Verhagen and Teunissen, 2012).
The validation methods are tested using data recorded at 12 International GNSS Service (IGS) stations in 80 one hour time periods. Based on the tests, the DNCF based rate ratio test is selected as the most promising ambiguity resolution method, and is enhanced through the addition of a number of checks including the time window based ambiguity validation and maximum carrier-phase lock-time specific confidence level selection to reduce the rate of incorrect ambiguity resolution.
In addition, the benefit of using both GPS and GLONASS to resolve GPS ambiguities is tested and quantified. Further tests include the analysis of the impact of the use of Numerical Weather Modeling based tropospheric corrections and the Imperial College Receiver Autonomous Integrity Monitoring (ICRAIM) method.
Based on these results, an optimal and state-of-the-art PPP model that addresses the current limitations is specified for the case of GPS and GLONASS L1 and L2 signals without external ionospheric corrections. The model is tested further using a dataset of 28 IGS stations located around the Earth for 80 different time periods. The general suitability and applicability of the new PPP model are discussed, and future research directions are recommended.
FENG, S., OCHIENG, W., SAMSON, J., TOSSAINT, M., HERNANDEZ-PAJARES, M., JUAN, J. M., SANZ, J., ARAGON-ANGEL, A., RAMOS-BOSCH, P. & JOFRE, M. 2012. Integrity Monitoring for Carrier Phase Ambiguities. Journal of Navigation 65, 41-58
GENG, J., TEFERLE, F. N., SHI, C., MENG, X., DODSON, A. H. & LIU, J. 2009. Ambiguity resolution in precise point positioning with hourly data. GPS Solutions, 13, 263-270.
LAURICHESSE, D., MERCIER, F. & BERTHIAS, J. P. 2010. Real-time PPP with undifferenced integer ambiguity resolution, experimental results. Proceedings of the 23rd International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS 2010). Portland, Or.
VERHAGEN, S. & TEUNISSEN, P. J. G. 2012. The ratio test for future GNSS ambiguity resolution. GPS Solutions, November.