Abstract:We analyze the activity characteristics of tropospheric delay in high altitude region by using ground-based GNSS observation data. The results show that the tropospheric delay varies significantly with altitude in the highland region, the accuracy of the Saastamoinen model is better than that of the Hopfield model, and the accuracy of both models at high altitudes is lower than at low altitudes, indicating that the performance of the conventional tropospheric delay model decreases at high altitudes. The mean values of total delay and wet delay at high altitude are 67% and 30% of those at low altitude, respectively, indicating that the adaptation of the dry delay part becomes weaker at high altitude and becomes the dominant factor affecting the model accuracy, which needs to be further optimized.