Research On Network Differential Positioning Technology Based On U-Blox GNSS Chip

With the continuous development of GPS technology,electronic technology,computer network and data communication technology,the navigation positioning chip tends to be miniaturizing and the application field of GNSS continue to expand,from the development in initial military field to the early professional surveying and mapping field,and then to today’s vehicle navigation positioning,logistics management,port scheduling as well as children’s positioning and other people’s daily life-related areas.As the GNSS positioning affected by a variety of complex factors,and people’s demanding for positioning accuracy is increasingly higher,simply using SPS service is not able to meet the needs for some users.For some users using small GNSS chips,through the serial port real-time to obtain differential correction data to correct the observed value can effectively improve the positioning accuracy and stability.The Continuous Operational Reference System(CORS)and Satellite Based Augmentation System(SBAS)are two ways to provide differential correction information services for GNSS positioning.In this paper,based on the development trend of existing mobile positioning technology and the advantages and disadvantages of various positioning technologies,discusses how to provide reliable,stable and high precision positioning service for GNSS users.Based on the understanding of differential positioning technology can effectively improve the positioning accuracy on the basis of CORS-based network differential positioning principle,working methods and error sources were analyzed.On the basis of researching RTCM data format,NTRIP communication protocol,and serial port communication protocol,combining the U-Blox GNSS chip with the existing CORS system,the serial communication of U-Blox GNSS chip and the programming of Internet network communication based on NTRIP protocol are realized on the computer.Real-time access to CORS differential correction data(TYPE1,TYPE2,TYPE3,and TYPE9)provide differential positioning services for mobile location devices by logging in to CORS server via network port and user password.The positioning accuracy and stability of U-Blox chip in three positioning modes based on CORS and Internet-based real-time pseudorange differential positioning(RTD)are tested by static and dynamic experiments.The results of this paper further prove that the accuracy of the positioning results can be effectively improved if the navigation GNSS receiver uses CORS network differential correction information for RTD positioning,which lays the foundation for the three-dimensional precision navigation and positioning.