Abstract：The determination of differential code biases (DCB) plays an important role in many GPS applications supported by code observations which include precise point positioning, ionosphere monitoring and the time transfer among GPS observation stations. The mathematical model for estimating the DCB is presented, which is based on the phase-smoothed code. The DCB for receivers of the reference station in CMONOC were determined with GPS observations of these stations in 2003, and daily and monthly variations of DCB were analyzed. It’s showed that the accuracy of DCB can be better than 1 nanosecond and the DCB of the reference station in the CMONOC have no remarkable variation during the time period considered.
