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Cedar Rapids, Iowa | There are several ways to transport RTK correction data such as via radios or over the Internet. The analogy to this is like writing a letter and putting it in the mail or faxing it. It still gets to the other place, but via different means.
There are also several data formats for RTK correction data such as RTCM 2.x, RTCM 3.x, CMR, CMR+. The analogy to this is the language that the letter is in such as english or spanish. Both the person sending and receiving a letter need to be able to understand the language they communicate in. I believe the Trimble 252 can accept CMR, CMR+ and CMR-w. The correction data goes into the receiver, gets merged with the GPS data to determine the position, and then position info goes out the other port in TSIP format to the Nav-II.
If you want to transport your RTK corrections from the tower to the rover over the Internet, I think that is going to pretty simple to do. Google for NTRIP Server and NTRIP Caster to see how that system ties together.
If you want to set up a Real Time Network where data from multiple base stations is merged to get better accuracy between base stations, then it is going to take some smarter software to do that, and probably isn't cheap. Trimble, Leica, and others offer software to do this.
When you use radio links to transport the correction data, you are in control of all the hardware. When you use the Internet to transport it, you are at the mercy of every provider along the path from your base to the rover. DSL lines are typically provided by the local telephone company, and your rover would be using a cell phone connection, which is commonly a different provider. On the back side of things, they may not talk directly to each other, but go through other providers along the way. The back end stuff is usually redundant enough that it won't go down. My biggest concern would be the DSL line (or what ever it is) at your base station. If that goes down, you can't get correction data until it comes back up.
-Lance | |
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Setting up a CORS network
