An Investigation on GPS Receiver Initial Phase Bias and Its Determination

摘要

This paper has described a method to investigate the existence, property and determination of the GPS receiver initial phase bias. The bias analysis has been conducted with respect to different GPS satellite and receiver conditions including receiver restart, satellite rise/fall and signal full loss of lock. The feasibility of initial phase biases calibration to support the ambiguity resolution in Precise Point Positioning (PPP) has also been investigated. rnThe method proposed for receiver initial phase bias determination includes two major steps. The first step is to employ two GPS receivers in a zero-baseline configuration mode to eliminate satellite related errors including the satellite initial phase bias so that the differential receiver initial phase bias can be estimated. The second step is to estimate the integer ambiguities on both L1 and L2 frequencies using the Geometry-Free (GF) phase combination and the resolved hybrid Wide-Lane (WL) ambiguity. The hybrid Wide-Lane (WL) ambiguity can be more easily resolved using code and WL carrier phase combination. To assess the reliability of the proposed method, the resolved ambiguity will be validated by comparing to the Double-Difference (DD) ambiguity obtained from direct rounding of the zerobaseline DD carrier phase observations. After the removal of the resolved integer ambiguity component from the GF observation, the inter-frequency receiver initial phase bias can therefore be determined. The Wavelet technique has also been applied to denoise the GPS observation data for improving bias determination accuracy. rnAccording to the experimental results using GPS receivers from two different manufactures, the existence of the receiver initial phase bias has been confirmed and its instability property in response to receiver restart and full Loss of Lock (LL) has been identified. As to the satellite initial phase bias, it can be calibrated due to its long-term stability, making integer ambiguity resolution possible in Precise Point Positioning (PPP) through between-satellite differencing of observations from a single GPS receiver