Abstract:In order to analyze the impact of the GPS satellite P1-C1 differential code biases(DCB) on the estimation of satellite-based augmentation system(SBAS) corrections, GPS C1-P2 dual-frequency measurements of the monitoring stations in mainland China are used to generate the GPS SBAS clock-ephemeris corrections and the corrections are used in a standard positioning test. According to the results, there are significant differences between the estimated satellite clock corrections with and without P1-C1 biases. The positioning results show that taking off the P1-C1 DCB during the SBAS corrections estimation and SBAS users positioning can reduce the GPS C1 code SBAS users 95% positioning errors from 1.94 m to 1.45 m and from 3.82 m to 3.14 m in the horizontal and vertical directions, respectively, indicating a 19% reduction in three-dimensional positioning errors compared to those not taking off the biases. For C1-P2 dual-frequency SBAS users, the P1-C1 DCB impact can be eliminated as long as the processing of P1-C1 DCB in users positioning is consistent with the SBAS corrections estimation.