Hello-
We are using 2X Reach RS+'s to gather GCP locations for use in drone mapping. One base, one rover. The base is running averaged single, standalone without additional corrections.
When selecting the GCP coordinate system in Pix4D, we select EPSG 4326.
What should we select for the vertical coordinate system?
Thanks for your help!
I think EPSG 4326 and WGS84 (what the Reach RS uses for BOTH Horizontal and Vertical coordinate systems) are the same. The same ellipsoid height.
I have never used Pix4D, but it may allow you to select other vertical coordinate systems or Geoids if need be? But seems EPSG 4326 / WGS84 would ideal for the most part since it matches the Emlid Reach RS’s?
Someone will jump in here hopefully!
Thanks Tim.
Here is what I see. What should I select/enter?
Thank you!
yeah, someone with real expertise here should help here as this will be important which you select… ; )
Great video!
Where on the Earth are you located?
Northeast USA, Philadelphia 
I would assume your are to be using NAVD88.
Not 100% sure though
Thanks TB.
This is all new to me, frankly. Is this setting determined by Reach when base is used in average single mode? How can I locate the definitive answer?
Here is more info from Pix4D:
Thanks!
Maybe the folks at Pix4D can help with the correct settings for your application, as I am not the one to ask about Pix4D “YET”. When I ever get time, I’ll be looking into all that, but don’t currently have a use for it.
MSD = Mean Sea Level
latest geoid:
https://www.ngs.noaa.gov/GEOID/GEOID12B/
https://www.ngs.noaa.gov/GEOID/GEOID12B/GEOID12B_CONUS.shtml
Reach reports height above WGS84 ellipsoid, so it looks like you need to enter WGS84 +0.00m in Pix4D.
Here is some good reading also.
https://support.pix4d.com/hc/en-us/articles/202559459-When-to-use-the-Geoid-Height-Above-the-Ellipsoid-Function-
Video very helpful:
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