NTRIP corrections datum: UNAVCO

I am trying to determine in what coordinate system the NTRIP corrections from UNAVCO GNSS sites are (so that I can choose the correct datum when collecting position observations and to later post process).

I contacted unavco at rtgps@unavco.org and they wrote back that their data are in ITRF 2008. However, this was not my question. I wanted to know in what coordinate system their corrections are broadcast (not their data, which can also be downloaded in ITRF 2014).

In the scenario that their NTRIP corrections are in the same coordinate system as their data, I searched for ITRF 2008 as a choice in my ipdad version of emlid flow. All I could find was ITRF2008 listed for Mexico. I am surveying in California (UTM zone 10N is not an option).

I am using an RS2 and have updated to firmware 3.1.

So, does anyone know in what coordinate system these UNAVCO NTRIP corrections are?

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First off, I would contact UNAVCO to determine their broadcast datum.

I know our states RTN broadcasts using ITRF2014 Ellipsoid as this was confusing to me on my first photo mission as I collected all my GCP’s in NAD83 E2010 coords (SC FIPS 3900). I was using my Autel Evo II PRO RTK for the mapping. I was using the states RTN for the flight as Autel only collects what is broadcasted (ITRF2014 Ellipsoid).

Your software in your controller converts the ITRF2014 RTN stream to whatever coordinates projection that you select in your controller for your project. In my case, I exported the GCP’s I collected to the RTN broadcast ITRF2014 Ellipsoid datum

I’m not sure what UNAVCO broadcasts, but I would imagine that it’s ITRF2014 Ellipsoid datum. One way to check is occupy a passive control mark that is in the NAD83 E2010 reference frame using the UNAVCO RTN. You can use the NGS Data Explorer to find a passive mark near your project. I would try and find one that was established fairly recently (<10 years old) with horizontal and vertical coords and occupy the station using UNAVCO RTN. Use an adequate observation length of at least 20 minutes. Then you’ll know for sure.

Good luck.


I have been told specifically that UNAVCO’s real time corrections reference ITRF2008. NGS’s tools say that for all practical purposes, ITRF2008 is identical to ITRF2014. Less than 3mm or something. In fact, the difference between ITRF2008 or ITRF2014 and current WGS84 is insignificant for general surveying purposes. Only fields using incredibly tight precision need worry about the difference. At least that is my understanding.

I have asked UNAVCO on a couple of occasions over the years if they plan to move to more current ITRF2014 or even ITFR2020 at some point, and have never received an answer. I don’t think the person responding to me really knows, to be honest. UNAVCO, now known as “EarthScope” by the way, is obviously a huge entity, but getting in touch with someone that actually understands the specifics of the geodesy side seems difficult.


Hi Jason,

Sorry for the late comments.

I agree with the guys. The best way to know for sure is to check it with UNAVCO themselves. When I reviewed data from them and compared it with the processing results from OPUS, I came to the conclusion that it should be something close to the ITRF2014. But as Dave said, it is similar to ITRF2008 or ITRF2020.

Which coordinate system do you need to work in? California State Plane? To get coordinates in the local projection with UNAVCO, I recommend doing a localization. You’ll need some benchmarks with known coordinates in the target CRS for it. Here is a guide with more details.

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