Community Forum

RTK Corrections for tractor auto steer project


So I am using the RTCM3 format currently with Slingshot.

“The RTCM 10402.3 standards defined the messages for differential correction information. There are 64 types of messages. The message format is a sequence of 30 bits. The messages 1 to 17 are available in older RTCM versions, while messages 18-21 have been added in version 2.3 to made the standard applicable to RTK corrections.”



And it looks like the Reach supports RTCM3 so the trick will be to figure out which messages are actually required to optimize bandwidth.



Anyone have any suggestions on a good cellular modem with highgain anttennas?


Ok sorry I missed an important part of your question here, I went back and grabbed another picture.


Diversity is a scheme where you usually have two antennas, and the device with antenna diversity will pick the best antenna of the two. That may change depending on which way the tractor is facing, etc.

…just came across a quote in their FAQ as well:

The way I read it, you have a base station somewhere (at your equipment dealer, or at your house) and that is connected to the Internet, so it can serve out RTK corrections (probably RTCM3). Then in your roving vehicle (tractor), you have a Slingshot field hub, which is basically a cellular modem with some extras. It has a GPS antenna, but that is not for RTK, only for reporting your location back to someone. The field hub must have some internal computer which can be set to log in to a NTRIP caster to get RTCM3 messages and then repeat them out the RS232 port. Your 750 must be taking those corrections in over RS232, and processing them against it’s own rover data.

Does that sound correct?

If so, then in the tractor, you would have:
Internet --> Cell modem --USB-cable–> Reach RS+ --RS-cable–> --Trimble-cable–> CFX-750

At the base station, you would have:
Reach RS+ --Wi-Fi–> Router --> Internet

(of course there could be a few variations on that)




How are the Reach M+ coming along?


Estimated ship date is on the product page:

I see it has been changed recently. That’s all I know.

(Jan Augustinov) #20

Hi, i am having the same issue, hope someone will find a solution for connecting the 750 on reach.


Waiting patiently for my Reach M+ to arrive so I can make this happen. :slight_smile:


Just got my Reach M+ in the mail.
Connected to device and am just sorting through settings.

Waiting on my cellular modem to show up.
ordered a Netgear LB1120-100NAS 4G LTE Modem.


Are you planning on having the Reach M+ act as your base, and then pipe corrections through to the Trimble CFX-750 (rover)?

If so I don’t want to burst your bubble, but I’ve run a similar setup with both Topcon and Leica receivers acting as rovers with Reach RS serving corrections from the base. Unfortunately it does not work.

On the other hand with an L1/L2 receiver at the base serving corrections to the Reach as rover then it should work, although we have found the fix to be a little slow and unreliable - although I don’t think this is what you are attempting to do.

Will be interested to hear how you get on.


Yes – I am planning to use one reach unit as the base station fixed in the farm yard. Planning on using a second reach unit in the tractors as the rover. Will pipe the corrections over to the CFX-750 via RS-232.

The current RTK system, the base stations stay on 24/7 but when you boot it up sometimes it can take upwards of 1/2hr to get a fix. But that doesn’t really matter as once it is up an running it should stay that way.

In Theory.


Ok have to rethink the modem.

This netgear one doesn’t come with wifi. WTF

Also need to have port forwarding ability…


Are you concerned with the lack of L2 on the Reach M+ for this application?


In your current system, your receivers on your rovers (tractors etc) should be getting an RTK fix within a few minutes if not well under a minute. Waiting 30 minutes to get a fix on a commercial RTK system, there is something very wrong there.

Secondly as pointed out above a Reach (base) to Reach (rover) connection will work fine, but I’ve yet to hear of a successful Reach (base) to third party L1/L2 receiver (rover) setup working. I’ve tried several different receivers now (TopCon, Leica, ComNav) and none of them remotely get a fix with Reach RS serving corrections from the base running ReachView 2.11.0. I’ve not yet tried with the new 2.14.0 stable release, but I’m not expecting any different results. So if you were to connect a Trimble/PacCrest radio to the Reach RS at your new base so it could serve corrections to your CFX-750 it in all likelihood won’t work.

Now for the second scenario with a ReachRS rover in conjunction with the CFX-750: as your CFX-750 has a full receiver built into the screen, if it’s unlocked for RTK you can feed it RTCM corrections directly via an NTRIP or via the internal/clip on Trimble UHF radio or serial port.

However connecting a Reach RS receiver to the CFX-750 will not help in this respect - the Reach will only be able to output an NMEA position/heading message stream serially. This is no use to the CFX-750 as it is already computing its own position (from its own GNSS antenna). Furthermore there is no facility to input an NMEA stream into the CFX-750 only for that unit output an NMEA stream. What it wants is RTCM (or CMR) based correctional messages - and as said if you feed it those from a Reach base it very likely won’t work.


Well that is disappointing that it will take 1/2hr to get a fix. May as well throw these in the garbage.

(Teltonika) #31

It is very random that I found this thread.

Trimble can get corrections via NTRIP and via RS232 with Teltonika RUT955 router. We have developed this feature so that RUT955 can be used as a link (Over LTE) between navigation device (Trimble, etc) and RTK base station.

However I am not sure if it would work with your setup as I understand only half of what you guys are talking here about.

Greetings from Teltonika HQ in Lithuania.

Can I get my thread unlocked please?
(system) closed #32

This topic was automatically closed 100 days after the last reply. New replies are no longer allowed.

opened #33