Problem with elevation

Hi !

I currently have a problem with elevation on Emlid receiver.
I’m actually not mastering GNSS technology so the solution of my problem could be very simple ! :slight_smile:

So, I work with a Trimble GNSS receiver (BX992) with a NTRIP corrections (Trimble VRS).
In the Trimble GGA frame, I found this kind of information : Orthometric height (MSL reference).

I think that this information is the elevation from the see level.
I currently found 67m with this receiver.
When I compare this value with online elevation map I think this value is OK.

Now, I get the same point with the Emlid Reach RS2 and I found around 110m.
It’s a huge difference :slight_smile:

I made some research and I have understood that it could be a datum problem but both receiver deal with WSG84 (I believe but not sure)

So, I hope someone could help me to resolve this issue.
Thanks you

Basically, Emlid gives you ellipsoïdal heights. You simply need to apply the geoid separation value to get the orthometric height.

You can look at this article for a quick explanation.
If you have several points, you can use an application like GPS-H and provide it a csv file to convert.


Hi Clément,

Welcome to our community!

You are right, it looks like the points were collected in different vertical datums. Our ReachView 3 app can provide either ellipsoidal or orthometric heights depending on the vertical datum chosen in the project. If I get it right that you collected the point with the Survey tool, you can tap on the project’s name to check the vertical datum.

Thank you very muh for your response.
I now use NMEA output of the RS2 and the elevation in the GGA frame is orthometric so it solve my problem.


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