Performance analysis of geometry-free and ionosphere-free code–carrier phase observation models in integer ambiguity resolution

摘要

Geometry-free linear combination of dual-frequency signal code and carrier phase observations have been used for multiple purpose such as to remove ionosphere-delays, improve the success rate in integer ambiguity resolution and accuracy in position solution. Out of three civil signals in GPS L1/L2C/L5 and Galileo E1/E5/E6, a user has many ways to form geometry-free linear combinations to solve integer ambiguity in carrier phase observations. In precise carrier phase positioning, probability of fixing integer ambiguities using code-carrier and carrier-carrier difference models rely on the ionosphere bias and code phase observation noise. When three frequency signals are available, the code phase observation noise can be reduced using ionosphere delay matched linear combination of carrier phase observations. Furthermore, the low noise smoothed code phase observations can be used to form a code-carrier difference model to fix ionosphere-free integer ambiguity. In this study, analyzed the propagation of observation noise and ionosphere bias in a geometry-free linear combination of GPS L1/L2/L5 code and carrier phase observations, i.e. ionosphere-free, wide-lane, extra wide-lane, medium-lane, and narrow-lane. Further, the feasibility and success-rate of using smoothed code phase observations in a wide-lane integer ambiguity solution is analyzed in precise positioning applications. Experimental validation is provided.