DGPS Data Formats And Research On Reference Station Algorithm

The real-time DGPS technique has been used widely in order to improve positioning accuracy and reliability. The DGPS system consists of three parts, which are reference station, data link and mobile station. It has been essential to transmit the information needed for DGPS computation from the reference station to the mobile station. So the DGPS data formats and base station algorithm are the two important problems of DGPS system.In this paper, three kinds of data formats including RTCM, CMR and RTCA, are introduced, and the development, message formats, information transmitted and bandwidths of this three kinds of data formats are described in detail. At the same time, several types of data formats being based on the RTCM, CMR and RTCM, like RTCM++, RTCM-Adv and CMR+, are introduced too. The same and different characteristic of the three kinds of data formats are compared, RTCM and CMR are used in LADGPS system, but the WASS of RTC A is used WADGPS; It's better to choose CMR data format in RTK because of CMR with less datum and quick positioning.DGPS reference station algorithm is discussed in detail taking example for RTK. Three types of algorithm for the generation of differential corrections and kalman model are described. On the base of the experiment, the algorithm used for RTK in RTCM is obtained by computing, analysis and comparison. The main message of types 18 and 19 is processed raw measurement And the differential corrections should be processed by Kalman filter for satellites' raise and descent can cause differential corrections' discontinuous change. The coding and decoding of RTCM message are realized using program.