| In recent years,with the rapid development of the differential satellite navigation and positioning,a lot of techniques have emerged out such as Real Time Kinematic and Network Real Time Kinematic.At the same time,the continuous operation reference station system based on Network Real Time Kinematic has been developed rapidly in the whole world.The related theories and techniques in this area have been applied to the real life and production applications.The differential positioning data transmitted in a continuous operation reference station system mainly refer to the rules of the RTCM protocol,transmit and share data and information in the Internet based on the Ntrip protocol.How to save the differential positioning data,encode and decode correctly,and transmit in the Internet efficiently and accurately is particularly critical for the practical application.After having studied the concrete content of RTCM protocol,the basic principle and the communication process of Ntrip protocol,this article mainly complete the following work:(1)Decode the data format of the RTCM protocol and design a new message type.Based on the RTCM’s encoding rule,we study the decoding process.In this paper,we design a new type in the blank message position combined with the pratical application,and finally get the general method of designing a new message type.(2)Implement the communication process based on the Ntrip protocol.Based on deeply analyzing the principle of Ntrip protocol and component elements,the communication process of the protocol is implemented by WinSock network programming technique and fulfill the requirements of the protocol.(3)Simulate the network model according to the theoretical model.Based on the classical model in Queuing Theory,we construct the communication network model and analyze the network performance according to the time of "customers" staying in the system obtained by the experiment with the network programming technique. |
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