Emlid

Community Forum

Elevation difference Question


(David T) #1

Hi

Reach working well, i have 2 RS+ units ( Base and Rover ), I have not issue staking out points so far. x and y value we very happy with. Howerever I have a question:

A land surveyor got a elevation on a point as 1427.13m M.S.L on a bridge nearby us.
I went to a old suveroy beacon nearby, whose cordinates I have. I got <30cm accuracy on Zaxis on that existing value.Which is acceptable.
I then to the bridge which they did a point on and I get 1424.88m M.S.L To reduce any discrepancy, I placed both base and rover directly on the curb about 1m apart. so there was no difference in height between them. I got a fix solution. So what could the difference be then?

https://drive.google.com/open?id=1gZ-xmepFXMKEfM7Ebqdd2iIW5megFRVO


(Timd1971) #2

First off, you DO NOT want to just place them directly on the ground like that in your photo!

Put them both on survey rover poles with a set height i.e. 2m rover pole is convenient. And enter the total height of pole plus thread adapter plus height to antenna (printed on bottom of RS+).

There are many posts abouts rover poles, tripods, rover pole tripods, bipods etc.

Recent post:


(David T) #3

Hi ,

Thanks, I did place on survey pole and tipod on previous try. I just placed on floor for a test, even sub meter accuracy do as test.


(Michael Lambert) #5

Here we go again with the ellipsoid vs geiod vs survey ground coordinates… 30cm is ok?


(Tatiana Andreeva) #6

Hi @dmterblanche,

I agree with @chascoadmin.

In the meantime, you can see only the ellipsoid height in ReachView. You can get orthometric height after post-processing, using RTKLIB. Check our GPS post-processing guide for it.