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changing elevation quickly

8 REPLIES 8
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Message 1 of 9
tmactom
322 Views, 8 Replies

changing elevation quickly

Hi all,

 

I conducted 2 surveys on different days and somehow the second survey was off by exactly 0.9 (don't ask because I do not know). With the temperatures being -10C with a very high windchill. I said I would worry about it after the fact once I put it into CAD. 

 

So I am on to Civil3D 2014. I imported the 2 .FBK files and was wondering how to do an elevation drop of 0.900m for just the one survey quickly.

 

Any insight would be great!

 

Tom

8 REPLIES 8
Message 2 of 9
Joe-Bouza
in reply to: tmactom

9 cm seems like an awful lot for temperature change no?

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Message 3 of 9
tmactom
in reply to: tmactom

More like 90cm (0.9m). I am sure it is just a user error as I am self taught on the Trimble GPS unit.

Message 4 of 9
ericcollins6932
in reply to: tmactom

Select the points to change, and right-click, datum, -0.9 to lower 9 decs.

 

If using RTK, I would want to know what caused the error and if it was from the first or second day rather than assume it was the second day.

0.9 error suggests a bad rod height (rod was set to 2.0, but wasn't raised to 2.0, for example).

Eric Collins, P.Tech.(Eng.)

Win 10
Intel i7 9700 @ 3 GHz
16 GB RAM
Civil 3D 2019
Message 5 of 9
tmactom
in reply to: ericcollins6932

Wasn't my first thought because I have that programmed in automatically (and I have a carbon fiber Rod), so raising and lowering it is no option.

 

Also, for some reason that option will not let me raise or lower the elevations...

Message 6 of 9
tmactom
in reply to: ericcollins6932

Woops, wanted to put in that the over lap from a previous job couple years ago was the same as my first survey. Leaving me to beleive that the second is the wrong one (I hope lol)

Message 7 of 9
ericcollins6932
in reply to: tmactom

Points are most likely locked in survey database Couple ways to fix as you brought in from field book. Go fix the rod height/base height in the raw data and re-import or fix in survey database.

 

An FYI and little advice, one should always have a check point on the job site to shoot at start and end of day and after base moves to ensure this doesn't happen.

Eric Collins, P.Tech.(Eng.)

Win 10
Intel i7 9700 @ 3 GHz
16 GB RAM
Civil 3D 2019
Message 8 of 9
tmactom
in reply to: ericcollins6932

Ya I just did that, thanks.

 

Like I said I am a self taught in Trimble so I am learning ways to tie points in around my Township so I do not run into errors like this. Any hints and advise always help a newbie like myself. I solely rely on these forums, Civil 3D book and videos.

 

Tom

Message 9 of 9
_Hathaway
in reply to: tmactom

While there are numerous wayts to QA/QC your RTK unit the #1 thing you want to do before you start acquiring any data is check into your control.  That means once you setup your base unit (assuming you run a base and not a network?) shoot at least 2 known control points.  If your coordinates don't match within your expected accuracies then you know something is wrong before you collect your data for the day.

 

I would be cautious of lowering all your data 0.9 unless you are 100% positive it's a global vertical shift.  SOmething has to happen, internally or externally, to cause this shift and you need to QA/QC to find it. 

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