Abstract:Positioning results may be influenced by different unavoidable errors such as space correlation errors,time correlation errors and so on,though ionosphere-free combination model can somewhat diminish the effects of ionosphere delay,and the orbit error can be modified more or less by the precise orbit.Based on the theory of precise point positioning,the paper presents a dscussion on the characterization of troposphere delay by adopting the data collected in different sample intervals,and also analyses of the variation of epoch-difference values of troposphere delay with the variation of sample intervals.Finally,the paper presents a study of the effects of troposphere delay on the observation of epoch-difference,the effects of residual errors on the position-difference and observation combination,and the variation of residual errors with time.