Setting Base Station with Emlid Flow "Meters"

[abhockle (Adam)]

I am using the Emlid Caster system with an RS2+ base station and an RX as a rover.

When I configure/set the base station RS2+ in Emlid Flow through the app, I am able to configure manually and enter northing and eastings. However, the elevation option is set only to meters. Is there no “feet” option went entering this information? Just wanted to verify. If it’s a no, then I must convert the elevation from feet to meters?

[zoltan.biber]

Hi Adam,

Emlid Flow can pick the coordinates of the base from a survey project. This way, you can use a position from a project in feet to set up the base. Please check this thread for the workflow.

[abhockle (Adam)]

So, I did this today. Imported a known XYZ benchmark in feet. The converted ellipsoidal elevation was 301.184 m. The benchmark height is 1070.050 ft.

However, when I convert 301.184 m to feet, I get 988.136 ft. That’s is not 1070.050 ft. I’m still kinda new at this, but does that have something to do with ellipsoidal heights?

I’m attaching the known benchmark coordinates and a control point that I created literally an inch from the benchmark showing a different height.

[abhockle (Adam)]

The X,Y coordinates were spot on. Just the elevation was off. When I created the project should I have left the “vertical datum” as defaulted? I selected NAVD88(GEOID18) as recommended. But I wonder if that is throwing it off. I may go back out there and experiment a bit.

[zoltan.biber]

Hi Adam,

The heights you compared are calculated from different surfaces. The orthometric height is calculated from a geoid, and the ellipsoidal height is from the ellipsoid.

After you choose your coordinate system for the new project, you can leave the vertical datum as default, and the application will calculate the ellipsoidal height. As an alternative, you can choose a specific geoid model to calculate the orthometric height from it.

You’ll need to set up the vertical datum of the project accordingly to the known coordinates of the base. If it’s NAVD88(GEOID18), choose NAVD88(GEOID18) and add the benchmark coordinates with the orthometric height.