Abstract:This paper calculates ZTD for Galileo, GPS and GPS/Galileo, with PPP ZTD estimation method using observation data from 14 MGEX stations. The RMSs of Galileo-GPS ZTD differences range from 8 mm to 16 mm. The average of RMSs of total stations is 12.3 mm, which proves that Galileo-ZTD agrees well with GPS-ZTD and that the accuracy of Galileo real-time ZTD is satisfactory. Meanwhile, IGS final ZTD products are adopted to assess the performance of each solution. The result shows that the accuracy is improved by 5%-35% when compared to GPS single solutions, and 25%-51% to Galileo single solutions.