Abstract: The methodology of VRS/RTK positioning,network correction generation approach and the Internet-based VRS data communication is presented.Field tests are presented to evaluate the performance of the proposed system.The results demonstrate that Inter net-based VRS RTK positioning can be achieved to better than 2.5 cm accuracy in horizontal position,and the height accuracy is in the range of 1 to 4.5 cm within the network.Distance-dependent errors,e.g.the ionospheric and troposhpheric delay errors,cannot been modeled effectively when rover receiver goes outside of the reference-station-network coverage area(up to 20 km in Chengdu,China),and the positioning accuracy degrades to dm level.