Reach RS2+ Settings with Trimble FMX1000 Rovers

Hello, few questions here about my new setup. I will go over our equipment first.
We have been running off of a local trimble base station for 15 years now with our tractors. Base station is surveyed in. Our 8 tractors are using trimble FMX1000 monitors running on rtk and glonoss unlocked. We have around 200+ AB lines we have created through the years and its important to keep using these lines in the future.

We now have switched to cellular VRS (sierra wireless modems) running off our our local caseih dealers setup through NTRIP. It all works fine but our lines have shifted 1-4 inches. Every field and every line is different. They all have shifted within the 1-4 inches.

I have now purchased a Reach RS2+ and going to run off of my own base station to cut down on subscription costs. As 8 tractors gets pretty pricey. I am in experimental mode now just connecting the tractors in the yard connecting to my mountpoint on my base.

Our Trimble FMXs will not run on anything but the Legacy messages. But having a hard time finding the sweet spot on the legacy HZ rate. And usually only pulling around 10sats on the trimble monitor.

Some of the questions I have:

  1. What is the best HZ rate for the legacy messages.
  2. Do I need to have my NTRIP Correction Input credentials entered in? That is the only way I can get a “fix” solution on the RS2+.
  3. Our old trimble AB lines created on NAD83…does that affect anything with this new RS2+.
  4. The way I am surveying in my base is adjusting the lat/long on the RS2+ until one of my trimble AB lines is near a zero offline distance. But I am sure it will be different on every field? I would think if I can get one line near zero then all the rest of the fields with ab lines would be close ? Or will I still have a line shift no matter what?

Thank you all for any suggestions and comments.

Hi @FarmerMP,

It depends on the rover update rate. If it’s not higher than 1 Hz, your settings look good to me.

Now it looks like the receiver is sending the corrections to itself. Not sure that it should be so, but I see the workflow as follows.

Your AB lines are collected in the NAD83 coordinate system. When they need to be re-surveyed by rovers from the new base, the base position should also be set to NAD83. You don’t have to keep the FIX solution on the base, just collect that point once in NAD83. Then you’ll set the base over that known point with the same NAD83 coordinates.

It sounds like you’re going from the opposite side because you’re adjusting the base position according to the rover position to get a match. Perhaps that’s okay for your scenario, but I’d try to tie base coordinates to the datum of the old bases you used when collecting AB lines.

Thank you for your replies. Yes that’s exactly what I am doing is working backwards to match the base with our AB lines. So how does one set the Emlid to NAD83 coordinates? I am all very new to all this base setup.

Hi @FarmerMP,

You need to create the project with a NAD83-based coordinate system and add or import known point(s) to it. When you go to the Manual mode of the Base settings, you can select the base position from the project:

Emlid Flow will do the rest: convert local coordinates into geographical ones.


So can I place my base on its permanent location then then do an average fix to get it’s coordinates. Then create a project in nad83 and then as you said add in those known points? This is all new…never created or done much in the survey tab.

Hi @FarmerMP,

In this case, you don’t need to add them manually. You can just collect points at these permanent locations in the proper NAD83-based coordinate system. Then you can pick them up from the project when you set the base in the Base settings.

Collected points become locations for your base, you don’t need to average them each time you set the base. Just make sure that these points are fixed and marked so that you can use them in the following surveys.

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