Trimble FM750 & Emlid Reach RS+ with Ntrip Caster

Good catch. The only signals a FM750 (Actually a CFX750 from Trimble, FM750 from CNH) can receive are US and GLONASS.

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Hi @jp-drain-sol, the legacy messages was definitely the solution to at least get RTK fix to the Trimble 750. What we’re now seeing is a low number of satellites when we have an RTK fix. When the fix drops (which we’re not sure if satellite issue or not), but the number of satellites does increase up to 20.

Any thoughts on this? Could it be a setting in the Trimble? Could adjusting the SNR mask on the base fix this?

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I had issues getting the GLONASS to work with my Trimble system. If I had the time I would tinker with my system. I’m in my busy season right now so not much spare time. I think that is why you’re seeing higher satellites with WASS and not RTK

If I have time to check my notes I need to see which GLONASS messages trimble is using.

The FM750 does not guarantee that you will get Glonass, there is an unlock for that too… only $616USD to unlock only Glonass… Really Trimble?

Buddies CFX750 is the same even off of a genuine trimble base, he has RTK unlocked but not Glonass. That’s why we are running away from that dumpster fire and switching to AgOpenGPS.

I am vary aware of the unlocks and their prices from Trimble. If you think that is bad lookup enabling GPS2 to RTK on a TMX.

Since he reported 18-20 satellites in WAAS it has to be unlocked. Most I have ever seen without GLONASS is 12 or 14.

I was using a FMX/FM1000 (RTK and GLONASS unlocked) with my M2 base/radio setup. When fixed, I was only tracking 8-12 satellites. According to the Trimble Online GNSS page, I should have had over 16. I was in open condition, no obstructions. When I checked which satellites where being used in AgRemote, none where GLONASS.

I haven’t been back to my project in some time now. Sometimes, life gets in the way.

The last thing listed on improvements, might be the ticked needed.

  • Added 1230 RTCM3 messages for RS2 and M2
    In the Corrections Output tab, you can find 1230 RTCM3 messages, which improve RTK quality with GLONASS enabled.
    I know Trimble uses that message.

Just an update that we did succeed with a 45km Baseline officially last night, never lost the signal. The biggest difference was the base station was placed on top of a shop with a much stronger wifi connection.

@jp-drain-sol, we’ll give the additional message a try and see if that does any further improvement.

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With NTRIP, you shouldn’t lose signal unless you lose internet.

How many satellites where you tracking? I am assuming just the U.S. not GLONASS. I am hopefull the new version permits our Trimble equipment to utilize them as well.

Good move, the base is imperative to see full open sky, if you cannot see the sats you cannot send corrections for them. Having the Base GPS antenna in an open area above buildings is a important step.

To even further improve long baseline performance learn to PPP (Precise Point Position) your base. It takes 12-24hrs of recording rinex data, then wait two weeks and submit to Nrcan to get the most accurate results.
The more accurate the base coordinates the lower the dilution error on long baseline measurements. Its easy to do this with Emlid, No extra unlocks needed!

Then never move your base antenna, and never change your input coordinates. You will be able to grain farm as accurate as a vegetable farmer, on the same tracks year after year.


Hi there,

Thanks for the discussion!

As @jp-drain-sol mentioned, on the 27 stable firmware, we added support of the 1230 RTCM3 message. It contains code-phase biases for the GLONASS constellation. This message may help phase ambiguity resolution on some 3rd-party receivers. As a result, the number of satellites used in calculations increases, the solution becomes more stable.

Please note that such an option is available on Reach RS2 and Reach M2 receivers only.

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we are using an emlid rs2 for base station and going through caster and our rovers are a trimble 750 and a fendt with a trimble reciever and factory auto steer
on the reach base app on base mode tab where we select which messages rtcm3 and legacy messages the base sends out to ntrip what should those be set at could someone specify, should they all be set to 1hz or more or less …

For any used constellation at 1hz is plenty for farming.

In north America the 750 is usually just GPS, unless you unlock each constellation individually. Only send the corrections for what you are using.

The arp coordinate message never changes in and should be set to 0.1hz or once every 10 seconds.

Make sure the 750 is set to wgs84, it will be a question in the rtcm3 setup.

And the legacy messages 1008 for Trimble also at .1 Hz? And antenna descriptors also at .1 Hz?
And gps and glonass at 1 Hz?

Does the Fendt also need to be set to wgs84? I don’t remember seeing it in Trimble 750 either but we are using that device plugged into back and the lefebure app to receive the ntrip corrections

1008 can also be 0.1, it was quite the dream getting that message out of an emlid and a feature request from this forum.

If the two tractors want to work together they have to interpret the datum model the same way. WGS84 is the stock setting but can be changed to many others, worth reading the manual about.

RTK set up improperly for farming still works awesome, If you get everything proper its almost a magic trick with multiple machines. Learn as much as you can about RTK from the surveyors on this forum, anything worth doing is worth overdoing.

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Hi Caleb,

Welcome to the Community Forum!

I see @PotatoFarmer has already answered your question. Just want to sum up: to use Reach RS2 as a base with the 3rd-party rovers, you need to output from Reach correction messages with the following frequencies:

  • 1006 ARP Station Coordinates, 0.1 Hz
  • 1008 Antenna descriptor and Serial Number, 0.1 Hz
  • 1004 GPS, 1 Hz
  • 1012 GLONASS, 1 Hz

1006, 1008, and 1004 messages are minimally required. You can also find more info on using Reach RS2 as a base in this guide from our docs.

The coordinate system of the rover should be related to the same datum as your base station.

I assume that you use Average Single to set the base. It provides your base with WGS84 coordinates. That’s why you need to set a coordinate system related to WGS84 on your rover as well.

Actually what we have is an rs2 mounted permanently on shop roof and connected to Wi-Fi. Have the base position set to manual and inputed the manual coordinates based of of doing avg. Single 6 times over , over a few days and using the avg. And now it’s set to manual. We need our AB lines the same year after year and the base may never move. Let me know if we did it wrong and should do it different

Did you create your AB lines with this setup? If so, you should have repeatability no problem. Once established with a base that doesn’t change, they stay solid unless the base data changes. If both bases are “surveyed” in, there should be little to no change in your AB lines.

If the AB lines where set from a different base or NTRIP that was surveyed in or not, your lines may shift whatever distance your manual base location is off from the previous base/NTRIP.


yes that makes perfect sense
we will be making all of our ab lines with this setup,
could someone clarify if we only have one base station and dont switch to any others does our own have to be surveyed in for our own use.

Hi Caleb,

I think that your workflow should work well. But I have a couple of comments.

For the tractor guidance, it’s usually required the relative accuracy only - the accuracy of the rover relative to the base. So to keep the measurements accurate from year to year, you need to fix the base position and note its coordinates achieved in Average Single.

You don’t need to Average Single position several times or do it again next year. Simply do it once, set achieved coordinates Manually, and don’t change them until you change the base position. Don’t forget to mark the initial base location if you want to move it but need to set it back later.

Just want to add that even though your base coordinates are set Manually, the way you achieved them is still Average Single. That means that they are in WGS84. So your rover coordinate system should be related to WGS84 as well.

One base should be enough :slight_smile: