Comparison of Observation Models and Ionospheric Elimination Approaches for Single Frequency Precise Point Positioning

Based on code,carrier phase and their combination so called GRAPHIC observation,three types of observation model for Single-Frequency Precise Point Positioning(SF-PPP) were presented,named as :"C-G model" making use of Code and GRAPHIC observation,"G-P model" making use of GRAPHIC and Phase observation and "C-P model" making use of Code and Phase observation.We considered two approaches to eliminate ionospheric effect : first,to remove the ionospheric delay with ionospheric map data from the International GNSS Service(IGS) which is the most accurate ionospheric model;second,to estimate the ionospheric path delay parameter together with receiver position,clock offset and so on.SFPPP experiments were carried out with static GPS data collected at 15 stations of IGS through day 75 to 90 in 2011 and airborne GPS data collected on September 5th 2008.It’s shown that different models and ionospheric elimination approaches lead to different positioning accuracy.Among all the three models and two approaches,G-P model and C-P model with estimation of ionospheric path delay,produce the best result for both static and kinematic positioning.Just saying the first ionospheric elimination approach,C-G model enjoy the best result.Our work indicates that,by adopt suitable observation and ionospheric elimination approach,an accuracy of a few centimeters for static positioning and several delimiters for kinematic positioning is achievable with SFPPP.