AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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Member
mrz999
Posts: 4
Registered: ‎01-17-2012
Message 1 of 10 (1,902 Views)

Creating an 3d alignment on a 3d surface?

1902 Views, 9 Replies
01-17-2012 09:25 AM

New to civil 3d?  Can I create an alignment on a surface so the alignment will value (follow) topo survey points on a surface.? My survey point are EX. elevation 600' to 700'.  When I create an aligment from a poly line our the aligment creation tool the alignment defautls to elevation 0'.  There for my feild stationing and CAD stationing is diffrent.   Any Ideas Thanks?

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dibr0804
Posts: 127
Registered: ‎06-29-2010
Message 2 of 10 (1,884 Views)

Re: Creating an 3d alignment on a 3d surface?

01-17-2012 10:28 AM in reply to: mrz999

Create a 3d polyline that runs through your points, then convert the polyline into a feature line, then create a profile from the feature. Or maybe you can just use the 3d polyline to get your profile without converting it to a feature line.

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WalterL
Posts: 29
Registered: ‎06-25-2009
Message 3 of 10 (1,859 Views)

Re: Creating an 3d alignment on a 3d surface?

01-17-2012 11:20 AM in reply to: mrz999

You can create a feature line (C3D 2012) from a polyline and have it add all the surface elevations to it, and then create an alignment from that.

Member
mrz999
Posts: 4
Registered: ‎01-17-2012
Message 4 of 10 (1,832 Views)

Re: Creating an 3d alignment on a 3d surface?

01-17-2012 12:59 PM in reply to: mrz999

WalterL

 

How do you create a alignment from a feature line? thanks

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SethHall
Posts: 723
Registered: ‎02-08-2010
Message 5 of 10 (1,823 Views)

Re: Creating an 3d alignment on a 3d surface?

01-17-2012 01:59 PM in reply to: mrz999

Alignments are only X Y objects, they do not have an elevation. If you have a surface created from the points, you can trace the points with an alignment, then sample the surface using the alignment creating a surface profile. Is this what you are looking to achieve?



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AllenJessup
Posts: 5,872
Registered: ‎05-21-2003
Message 6 of 10 (1,795 Views)

Re: Creating an 3d alignment on a 3d surface?

01-18-2012 06:54 AM in reply to: mrz999

Alignments are 2D. You can create a Surface from the field points and then create a Profile from the Alignment and Surface. I think you can extract a Featureline from the Profile. If not you can create a Corridor with a single Assembly and extract a Featureline from that.

 

But that doesn't seem to address your need. You seem to want to run stationing along a 3D surface. I don't think that's possible in any program I've heard of.  In nearly 30 years of Surveying and Engineering, I've never heard of this being done.

 

Allen

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engrtech
Posts: 730
Registered: ‎05-05-2008
Message 7 of 10 (1,786 Views)

Re: Creating an 3d alignment on a 3d surface?

01-18-2012 08:44 AM in reply to: mrz999

I've always wondered why a 3d polyline isn't used for an alignment and profile.  Seems like it would be easy to have one object that does both functions. It wouldn't be hard to program a way to view the 3dpolyline as a 2d line in plan view and a side view for a profie.  In the case of having a need for two profiles, just have another 3d polyline that has the same horizontal coordinates but the vertical is different.  

 

Seems like then it would be easy to use a sweep (Is that the term? I'm used to 3ds Max's loft) of a road assembly section in order to get a corridor. This could also be done with basic, Autocad objects, which means no versioning problems and could be backwards compatible, not to mention easy for 3rd party applications to access the objects.  

 

Of course, I could be completely wrong about my idea and that alignments have to be 2d for some reason I just don't know about.  

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Distinguished Contributor
josephbouza5497
Posts: 107
Registered: ‎11-29-2007
Message 8 of 10 (1,762 Views)

Re: Creating an 3d alignment on a 3d surface?

01-18-2012 02:46 PM in reply to: mrz999

Um just a dumb civil engineer. I curious why you want a 3d alignment?

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n2itive
Posts: 104
Registered: ‎04-15-2003
Message 9 of 10 (1,742 Views)

Re: Creating an 3d alignment on a 3d surface?

01-19-2012 06:32 AM in reply to: mrz999

Hmm... so if you're using a 3d alignment and stationing how would someone in the field calculate a random distance or elevation from the plan&profile sheet? I know technology has come a long way but contractors still need to do some random dimensions or scaling every once in a while. If your alignment and stationing were 3d then your profile grid lines would be at random intervals based on the slope of the profile (or alignment in this case). The steeper the slope the closer the grid lines spacing would be.

I don't  think it's a question of why it's not possible (in a computer programming sense) but instead has to do more with common practices within the industry.  

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engrtech
Posts: 730
Registered: ‎05-05-2008
Message 10 of 10 (1,731 Views)

Re: Creating an 3d alignment on a 3d surface?

01-19-2012 08:12 AM in reply to: n2itive

Feature lines have the 2d length property as well as the 3d length property.  I don't know why a 3d polyline couldn't have the same properties since they are essentially the same thing.  The stationing would be based on the 2d length, so it'd be no different than it is today.  But, there could be the option to get 3d stationing if for some reason someone needed it for a physics calculation or some other reason. More options are better than none.  

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