Precise frequency transfer model suitable for short baseline link based on GPS single-differenced observations with ambiguity resolution

A frequency transfer model that is suitable for short baseline links is proposed herein. Based on a GPS single-differenced (SD) observation among two stations, the initial values and the corresponding variance of the SD ambiguity can be estimated. This can form the double-differenced (DD) ambiguity while defining the reference satellite, and can be fixed to an integer value by using the integer search method. After defining the values of the SD ambiguity datum for the reference satellite, the other SD ambiguities can be recovered; then, the final time difference of the two stations can be estimated using the known and fixed SD ambiguities. Validations performed using five different baseline links show that the new method has better accuracy and stability for precise time transfer than the traditional precise point positioning method, and it can be operated in conjunction with the broadcast ephemeris data, which is more convenient for real-time application.