AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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Contributor
AbsKelvin
Posts: 11
Registered: ‎01-19-2011
Message 1 of 7 (801 Views)
Accepted Solution

Flat surface contours, sporadic and unpredictable

801 Views, 6 Replies
12-02-2011 12:21 PM

I often have to do storm pond surfaces that (for the purposes of planning) are flat on the bottom. These surfaces are created from a combination of survey data and grading groups and the tin of these surfaces is perfectably acceptable. However, when contours are shown, the flat bottom is shown with contours jig-jagging all over the place.

 

The attached image shows a comparison of the same pond. The top was created with survey data and grading groups; the bottom was created using contour data only. The generated surface on the top shows the bottom contour going in different directions and has parts where the an expected contour is missing.

 

Any ideas on how to correct/manipulate the surface to show a proper flat surface?

 

Thanks!

Kelvin

You might be able to get away with adding a point of two to the middle of the bottom that is 0.01 feet lower than your bottom contour.  This might get rid of the flat area (that could be causing the "jig-jagging"), but it won't be low enough to change volumes or add an additional unwated contour line.

Active Contributor
nvengineer
Posts: 29
Registered: ‎04-05-2010
Message 2 of 7 (783 Views)

Re: Flat surface contours, sporadic and unpredictable

12-02-2011 01:46 PM in reply to: AbsKelvin

You might be able to get away with adding a point of two to the middle of the bottom that is 0.01 feet lower than your bottom contour.  This might get rid of the flat area (that could be causing the "jig-jagging"), but it won't be low enough to change volumes or add an additional unwated contour line.

Contributor
AbsKelvin
Posts: 11
Registered: ‎01-19-2011
Message 3 of 7 (768 Views)

Re: Flat surface contours, sporadic and unpredictable

12-02-2011 03:12 PM in reply to: nvengineer

That clears up a lot of frustration. I was thinking I was missing an obscure setting, but this is a easy workaround. Many, many thanks!

*Expert Elite*
MarySeufert
Posts: 581
Registered: ‎04-19-2011
Message 4 of 7 (767 Views)

Re: Flat surface contours, sporadic and unpredictable

12-02-2011 03:36 PM in reply to: AbsKelvin

Hi Kelvin,

 

Try this, under Prospector->Surfaces->(Your Surface)->Definition->Edits, if multiple edits exist, delete them one by one starting with the first listed (oldest). This will get rid of interpolations that C3D added as you created the surface, which may now be interfering with newer data and causing the weirdness. This has worked for me with similar looking surfaces.

 

~ Mary


_______________________________________________________________________
Normal people believe that if it ain't broke, don't fix it.
Software Engineers believe that if it ain't broke, it doesn't have enough features yet.
*Expert Elite*
MarySeufert
Posts: 581
Registered: ‎04-19-2011
Message 5 of 7 (766 Views)

Re: Flat surface contours, sporadic and unpredictable

12-02-2011 03:38 PM in reply to: MarySeufert

Nevermind, you found a way while I was away from my desk! :smileyvery-happy:


_______________________________________________________________________
Normal people believe that if it ain't broke, don't fix it.
Software Engineers believe that if it ain't broke, it doesn't have enough features yet.
Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 6 of 7 (600 Views)

Re: Flat surface contours, sporadic and unpredictable

10-31-2012 04:51 PM in reply to: nvengineer

I've come across a variation on this solution that will help with more complicated areas. Instead of just adding a point with a slightly lower elevation, consider offsetting the feature line of the toe of the slope and adjusting the elevation of that feature line by a small value. This helped fix my rather complicated/narrow flat area (whereas the point approach required many points to make the contours right...)

 

cheeers.

 

-d

Mentor
mikepo
Posts: 239
Registered: ‎04-29-2008
Message 7 of 7 (317 Views)

Re: Flat surface contours, sporadic and unpredictable

12-31-2013 01:38 PM in reply to: eladkcem

We had this same issue just now and after some out of the box thinking we found something that worked.

We were trying to grade to elevation 271.00 with 1' & 5' contours for surface display and the 271.00 contour was all wonky.

Edited the grading to 3 decimal places (270.999) and when the grading rebuilds, the surface contours are fine and showing a flat surface.

Mike Porter
www.ppeng.com
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