RTK radio link


New to AgOpenGPS and GPS for tractors. I have been looking at this forum and have not been able to fix the connections between the caster and rover. I just bought simpleRTK2B – Starter Kit XLR from Arudsimple and have been trying to get the RTK on AgOpenGPS (Radio link). I have used the U-Center software and I think I get corrections under the UBX-RXM-RTCM Message view window. Apparently, I don’t have to do anything at the AgOpenGPS software but I am not getting any RTK signal. I have read that the Caster has to be up for a while. Some say 1500 messages. How long is this or where can I see the count of messages? Since I could see the RTK data on the view window on U-Center software, does AgOpenGPS wait for Caster to send all the messages first? Right now, I am using it as a test to get everything right before I put it on a tractor. I have them close to each other and connected to a desktop. Like I said, I see RTK data on the rover. At least that what it seems. Can anyone that uses this setup give me some instructions on how they got their setup to work?


When you say you can see the RTK data in u-center, are you talking about the rover or the base receiver? Normally when using radio modules, the radios are connected directly to the F9Ps on uart2, and AOG is not involved at all. When you connect u-center to the rover, do you see RTK fix or float in u-center? Or does it stay at “single?”

Hi torriem,

At the rover, when using the u-center program, this is where I get the data under UBX-RXM-RTCM Message view window. I do not get anything when looking at the caster in the same window. At the rover, when I turn off the caster, I quit getting the data that I see when both are on. I will have to get my setup running so that I can look at what you are saying about the “single” and post it.

Sounds like the rover is getting the data then. Are you GPS antennas outside where they have a clear view of the sky?

Hi Torriem,

In AoG, I get the Quality: GPS Single. Is this what you mean? Thinking about the simpleRTK2B – Starter Kit XLR that I bought (radio RTK transfer), would the position that the rover gives( having the base transmitting the RTK) have the RTK corrections applied to it? Meaning that it will be the precise location within cm’s or does it mean that it needs AoG to combine both data (GPS receiver and RTK from base) to interpret the precise location (cm accuracy)? If the rover receives RTK from base, how can we plug in the received RF (RTK correction) data to AoG (RTCM port)? I bought the mentioned kit because I thought that I would not need any NTRIP cost and I am a little out of cell range. I also read that I need to create a 24 hour log for the base and send this log to some place for them to give me the correct location of the base. Do you know how I can log this and where do I need to send this log to get the location of my base? Any help will be appreciated. I am still reading but I also get confused sometimes.

Hi Torriem,

I left the AoG running for a while and not where it said Quality, now I got Quality: DGPS:

Should it be doing this?


Once your base is configured for an accurate location, the rover GNSS receiver gives cm accurate data as long as it is receiving RTK correction data from your base. AOG is not involved, not even to deliver RTK corrections as you do it via radio.

Here seems to be a detailed guide to obtain accurate base coordinates (have not tried this myself):

Right. With the radio modules, there is no need for NTRIP or for AOG to be involved at all. As long as the rover is receiving messages over radio (via UART2 pins), it should be able to achieve RTK on its own, and the signal reported in U-Center or AOG should be RTK Fix. Only U-Center is required to connect to the receivers to configure them and to figure out why RTK is not happening. Once you can get RTK, then you can fire up AOG and it will just see your RTK GPS.

It is not necessary to do a 24-hour log of the base station, unless you really need your RTK setup to match someone else’s coordinates. For our purposes it is enough to have the base station do a “survey-in” for a few minutes to find its approximate location. After that your rovers will be relative to the base station within a few cm. And if your base station is permanent on a shop or something, you can manually set the base station lat/lon/altitude coordinates with u-center (I based mine off the initial survey coordinates) so that your lines and fields will never shift year to year.

There are lots of tutorials online for setting up the base station, including the one @NorthernFarmer linked to. Here’s another one: Setting up a Rover Base RTK System - SparkFun Learn. Follow the bits about using U-Center. It does not matter whether one is using ntrip or radio; the base station setup is the same.

Other than setting the NMEA messages you need and their frequency, there is no configuration you need to do to the rover F9P to get RTK.