NRCan outputs NAD83(CSRS) or ITRF, not WGS84

Regarding this tutorial here:

I think there is a bit of a mistake or lack of explanation regarding the NRCan CSRS-PPP results. The results are output either as NAD83(CSRS) or ITRF. The vertical datum is CGVD2013. These values cannot simply be input as a fixed point for your base station in Emlid Flow, because Emlid Flow is using WGS84. I think the vertical meters value is meters above the WGS84 ellipsoid?

For this to be correct, the results from the CSRS-PPP results needs to be converted. Though WGS84 is close to ITRF, I do not think it is exactly the same. Maybe I’m wrong?

It is my understanding that for cm precision, ITRF can be considered equivalent to WGS84.

1 Like

The main difference between ITRF and WGS84 reference frameworks is the choice of fixed stations used in their adjustments. Not surprisingly, the difference between WGS84 and ITRF 2000 is now very small, generally less than 10 millimetres.

Datums Explained in More Detail | Intergovernmental Committee on Surveying and Mapping.


I see, thank you for the clarification.

In Emlid flow, if I need to be working in NAD83, and I am using NRCan, I should still be using ITRF to set the fixed position of the base station, because that input is WGS84, and the app will translate points accordingly?

Inputting a NAD83 position would actually be wrong, because Emlid Flow will make the appropriate translation for you when taking survey points, based on whatever datum / CRS you set for the given survey?

Here you go, this should clarify

No, Emlid Flow will only translate resulting coordinates, not the base coordinates.

That is also why you will see a warning when entering the base coordinates l, that your coordinates must be in the same frame of reference to the selected coordinate-system in Emlid Flow.

1 Like

Hi Nicholas,

This should be pretty straightforward. You set the base coordinates obtained from NRCan in NAD83, select the project coordinate system based on NAD83 as well, and the rover calculates its coordinates in NAD83 datum. WGS84 isn’t involved in this configuration.

I can second these Christian’s words. I assume that you’re located in Canada, so you can check how this point is described in our docs.


Thanks for all of the clarification, very helpful!

It sounds like whatever datum the base is set with, be it manual or NTRIP needs to be the same as what points are for the rover. If the survey is in NAD83, the manual point for the base should be the NAD83 coordinate. Likewise, if the survey were in WGS84, the base would need a manual WGS84 / ITRF coordinate.

In California, for example, UNAVCO NTRIP stations output in ITRF, but surveying in California needs to be NAD83 State Plane. This combo wouldn’t work in Emlid Flow, unless I manually convert the NTRIP coordinates to NAD83.

1 Like

This is just like our RTN in SC. It broadcast ITRF 2014 data but in your software you can select the projection SC NAD83 (2011) Epoch 2010 cords.

I flew a site with my EVO Pro V2 RTK just for practice learning AgiSoft Metashape back in March. The Evo was in RTK mode collecting only ITRF 2014 as that’s what Autel uses in their UAV’s. This is also what Metashape uses for processing the imagery but you can export to any projection in their software. It’s kinda weird the way Metashape converts to whatever datum/projection but it works when exporting the surface dem/ortho data

I collected all my GCP’s in SC NAD83 (2011) Epoch 2010 cords. I should have set the collector in the same datum as the UAV. But our software in the controller for the rover can be exported to the UAV datum.

This was using my Javad Triumph Victor LS system. I wanted to use my RS2 but I had some issues connecting with it. I’ll try and use my RS2 next time.