AutoCAD Civil 3D General Discussion

Active Member
Posts: 10
Registered: ‎01-25-2013
Message 1 of 6 (411 Views)

Datum Surface not Consistent

411 Views, 5 Replies
01-29-2013 06:13 AM

Anyone know why a Datum Surface will correctly follow the bottom links of a corridor at 1 location but not another?


Please see attached.  The 2 stations shown use the same assembly and are in the same region. Some locations appear to be correct, while a few other locations "skip" points they are supposed to hit.

*Expert Elite*
Posts: 2,767
Registered: ‎11-13-2006
Message 2 of 6 (392 Views)

Re: Datum Surface not Consistent

01-29-2013 08:19 AM in reply to: cman24

Did you toggle the overhang correction to 'bottom links'?

John Mayo, PE
IDSP 2014
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Active Member
Posts: 10
Registered: ‎01-25-2013
Message 3 of 6 (389 Views)

Re: Datum Surface not Consistent

01-29-2013 08:22 AM in reply to: cman24



I am hoping I am just missing something simple like that, but I just can't figure out what it is.  It wouldn't be so frustrating if the error occured at every location, but the fact that it works at some and not others is just confusing.

Posts: 256
Registered: ‎10-31-2006
Message 4 of 6 (357 Views)

Re: Datum Surface not Consistent

01-30-2013 07:46 AM in reply to: cman24

If you look at the surface triangulation in plan view you will probably see that the tin lines are not created correctly along the vertical portion of the datum.   Two ways to fix this:


1. Reduce the frequency distance.  This will output more link data to the surface, which should cause the triangles to form correctly between the adjacent corridor sections.


2. Or, add feature lines from the top and toe point codes.


David Zavislan, P.E. | Wood Rodgers, Inc.
Posts: 708
Registered: ‎08-25-2009
Message 5 of 6 (348 Views)

Re: Datum Surface not Consistent

01-30-2013 08:46 AM in reply to: david.zavislan

What subassembly was used to create the curb? It looks like you have three points at the same place vertically and this is causing the TIN "issues". We've tried to make our internal subassemblies have a very slight offset (moving to away from the centerline) to avoid these conditions.




Peter Funk

Autodesk, Inc.

Peter Funk
Autodesk, Inc.

Active Member
Posts: 10
Registered: ‎01-25-2013
Message 6 of 6 (336 Views)

Re: Datum Surface not Consistent

01-30-2013 02:33 PM in reply to: cman24

This is a subassembly from our Client (WisDOT).  I've experienced issues before related to the vertical stacking of points.  There is a slight offset with this subassembly, but maybe it's not enough of an offset.  I just found it odd that it worked in some locations and not others.  I think I will just have to apply a work-around like what David suggested until I can get an update to this subassembly.


Thanks for the help.

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