Ortho Heights for Surveying a River using 2 Reach RS+

Hy everyone!
This is my first time using Reach RS+ so bear with me, please!
I’ve recently started to manipulate 2 Reach RS+ and planning to potentially using them on the field soon! However, I’ve encountered issues regarding orthometric heights, information I definitely need to use for comparison purposes with older surveys.
My plan is to use both RS+ and also a Phantom 4 PRO, create ground control points on the river and get info from elevations using the Structure from Motion procedure. Therefore, is extremely important that I get accurate information on the heights. The river itself was affected by a landslide some years ago and there is still some material deposited on it…so we want to calculate volumes of sediment between two different epochs…but still not sure if my emlids would be able to get accurate values of ortho heights that can be comparable with older surveys (performed using other equipment).
In fact, I tried it out some days ago but seems to me I am only able to get ellipsoidal heights. Also, the area I will go to is very remote so it is likely no benchmarks are available. So definitely RTK is my first option (since I have2 RS+). However, the ellipsoidal height is not something I am looking for… Perhaps I am missing something?
Thanks in advance for your help. And happy to give more details if needed.

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Hi @mishelm2,

Thanks for describing your workflow in detail!

Just wanted to double-check, are you working with ReachView 3 app? There, you can choose the required coordinate system and vertical datum so you don’t need to operate the geographical ones only. We have a doc that describes how to set up your coordinate system in ReachView 3.

Also, as you need to survey your points with absolute accuracy, I suggest paying closer attention to the way you set up your base. We also have a Placing the base guide that explains different variants of placement.

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