Set up own Trimble RTK base for Emlid rovers


We have an issue at one of our sites which is located in ~20 km distance from the two nearest base stations from the VRS network. It often causes very poor RTK connection and 20-30% of all the points end up having only RTK Float. We are thinking of setting up our own permanent base station somewhere in the middle and use Emlid Caster service if possible. The key requirement is that the setup shouldn’t ask for a lot of maintenance. We have several Emlid RS2/RS3 which are used as the rovers and we also have one Trimble Zephyr antenna and the SPS logger (don’t remember the model of both). Is it possible to setup the own base configuration using Trimble as a base and transmit the corrections to the Emlid rovers via Emlid caster? We need to have it running it all the time so the RTK corrections are available on any working day.

If anyone has done similar things, I really appreciate any info regarding this matter :slight_smile: I do not know much about setting up a base but with enough info provided I can try doing it myself.


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Hi Mykola, try this one

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You might want to first look at the specific SPS receiver and Zephyr antenna models you have to confirm that they are going to meet the basics of what you need as there are a lot of variations.

For example, some earlier SPS & Zephyr models are GPS & Glonass only and won’t provide corrections for the other constellations supported by RS2/3 which could be limiting in certain environments.

Ours is SPS850 and Zephyr Geodetic antenna. According to the specifications, this kit should provide everything we need I suppose. I am interested in knowing how to set up the base so it can broadcast corrections to our Emlid rovers. Also, we need the correction to be in the local coordinate system ISN93.

That confirms you definitely need to do your basic homework first.

The SPS850 is GPS & GLONASS only. You don’t say what version Zephyr Geodetic you have but presumably then it’s a model 2 which is also GPS & GLONASS only.

And you will need to confirm if the GLONASS & RTCM options are actually enabled in the SPS850. E,g. if they were purchased in that particular configuration you have.

You will also need to confirm your current SPS850 firmware version and whether it’s high enough to have survived GNSS Firmware Week Number Roll Over (WNRO), the latest iteration for Trimble was in August 2023.

Then presuming all of that checks out, have you actually tested yet if GPS & GLONASS only is sufficient for your workflow and GNSS conditions you are operating in?

Trimble gear is very powerful but can be very complicated to set up if you are not used to it. Setting up an RS2 instead would be quicker & easier, all the support you need is right here and with full constellation corrections provided will give you better performance at the Rovers.


The kit was laying on a shelf for many years so I doubt it was updated recently. I have to check if GPS and GLONASS are sufficient. After reading the emlid docs, using emlid seems easy and straightforward even for the base setup. We were thinking of setting up a permanent base on top of our office in the are without a good coverage. But if that process is complicated and requires a lot of tech knowledge then we perhaps have to wait before the local RTK service provider puts another base in that area to add to there VRS network.

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I test configured a NetR5 UHF base to use Emlid Caster and it worked fine. Setting up an RS2 would definitely be easier for the uninitiated though.

For posterity for anyone else who may stumble in here this is how it’s done, the interface in most Trimble modular receivers should be similar.

Pick any of the NTRIP Server lines:

And this is how it’s configured. Enable RTCM and disable the rest:

And so long as you have internet you are good to go, Emlid Caster is being fed:

And the RS3 is happy:


We are using a rs2 on our office as a base and using the Emlid caster to send the corrections to the rovers it is very straightforward and the Emlid page has good documentation on how to go about it get a external power cord and antenna and your set


We run a NetR9 as a community base station and as part of Trimble’s RTX network, and use its NTRIP caster function similar to what Wombo showed w/ their NetR5. It is nearly maintenance-free. I think we went 8 years or something w/o a reboot until a bit less than a year ago. Current uptime is 247 days.

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Thanks for the detailed steps. Greatly appreciate it. I will try this along with the Emlid-only base. I know it should not be a big deal but I have never done it so the learning curve is quite steep. Cheers.

Apologies for possibly a dumb question (coz I suppose I should know it) but when the base is set up, in what CS the corrections are sent? Another questions:

  1. How do I chose in which CS the corrections from the base should be? Coz with the commercial RTK service I do not have to think about it.

  2. If I choose an unknown point, can I determine the location with high accuracy by collecting and processing the data for further use as a reference point for the same base? Let’s say if I cannot set an intermediate base half-way between myself and the nearest reference station due to the large distance, can I establish a “known point” myself?

Also, any good online course on the GPS data and processing? I have a degree in geophysics but never fully dived into GPS techniques.

Thanks, it was pointed out several times that this solution could be the easiest to implement. I will surf through the docs for further info.

You guys rock! Thanks for info, I will try to play around with our devices and hopefully it works out with a little effort.

OK, all good questions.

  1. Some may disagree but the beauty is that the corrections are not locked into a datum. The base coordinates could be anything, no datum is defined in the RTCM messages and that can cause confusion so you need to know what it is, but in a controlled and well managed environment they can be whatever makes sense and promotes consistency and it’s great. For example, here in Australia (like many other countries) our base coordinates are certified in our national datum. Here that’s the GDA2020 datum so wherever we are, whatever we do, we configure everything GDA2020 and all the corrections are relative to GDA2020 and everything is consistent, and life is good. You will obviously need to check for your own country and providers.
    The disclaimer here is that in some special situations that is not true, e.g. survey custom site-specific coordinate systems, scientific geodetic work, a mine survey where the vertical datum point is set very deep so there are only positive numbers etc. Just trying to keep it simple for you to start with.

  2. Yes, you can absolutely calibrate your own reference points, it’s very common and most of us do it. Often it’s done via a process called PPP and there are plenty of tutorials, start here: How PPP works | Reach RS2/RS2+ ( In Australia we use our own service called AUSPOS (it’s not PPP) and get the results in, wait for it, GDA2020, but they also provide precise coordinates in ITRF2014 (google it) which apply for anywhere in the world. So if you used it you would only need a local tool or calculator to transform those coordinates once into your local datum or whatever datum you are using.
    And when you set your base up simply use those coordinates.

I don’t know myself of any particular online course, I started growing into this before the internet so someone else may have a suggestion.

Otherwise, there is an enormous amount of explanatory information out there, much of it is very technical but sometimes in plainer language. With enough sniffing around you will eventually come across something at a suitable depth and language style that works for you so stick with that and if you encounter any tricky concepts branch off and follow those terms up separately. In line with their target market EMLID are good with basic explanations that are consistent with their specific product nuances so start here first.


Thanks a lot for the detailed info. All the answers here are very valuable and now I learned a little more :+1:

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