Abstract: Components of observed GPS pseudo range are analysed.A real time data collection system is designed.SA error signal is extracted by positioning computation and filtering clock bias.Testing result points out that the SA error is basically a stationary stochastic process with zero mean.AR(13) model is identified for SA error with the data collected in a fixed location during a period of time, and then a great deal of the model parameters are obtained. Some useful conclusions are derived by analysis of model parameters in the time domain and frequency domain.

Key words: GPS, SA, time ser ies, positioning, filt ering, modeling