Ntrip protocol
In the RTK receiver, there are many ways to obtain differential data: radio, external serial port, network, etc. Among them, the network mode is suitable for areas with network base stations, saving the need to carry one more RTK receiver to complete the work.
CORS is a network reference station, which transmits and receives GPS differential data through the network. After the user accesses CORS, the differential positioning of the GPS rover can be realized without setting up a separate GPS reference station.
To access the CORS system, a network communication protocol is required. NTRIP is one of the communication protocols of CORS system.
See the flow chart of the entire visit below.
I don't want to expose the content and details of the work too much here. In fact, the cors server does not have high requirements for concurrency, because generally speaking, there are not many devices connected online to obtain differential data at the same time. The software framework of single server + single process select IO multiplexing model + multiple worker threads can meet the business needs need.
The figure below is a simplified version of the server. In practice, for efficiency and data stability, thread pools, memory pools, and heartbeat sensing mechanisms are introduced to optimize non-blocking io. For data processing, there are tcp sticky packet loss processing (adding packet header + second cache mechanism), logging, etc.
