## AutoCAD Civil 3D General Discussion

Valued Contributor
Posts: 56
Registered: ‎08-07-2012
Message 1 of 12 (491 Views)

# A very basic question about surfaces

491 Views, 11 Replies
02-06-2013 03:21 AM

Hello.

I am trying to learn the Civil 3D, but it is more complicated than i thought. Signed in for some lessons, but until then, i am trying to learn it on my own.

I want to draw a river bed out of nothing. Then draw the water surface. Then find the volume of water in given river.

Where should i start and what should i keep in mind?

Is it possible to just draw the river bed and make a TIN surface out of it using 3Dfaces, then do the same with water surface and then find the volume between those two surfaces?
Or am i missing something very basic?

EDIT: I understand this may be too much to explain through the forum, but if i could get any hints what to search for in google, i would appreciate it.

Mentor
Posts: 186
Registered: ‎12-02-2009
Message 2 of 12 (470 Views)

# Re: A very basic question about surfaces

02-06-2013 05:06 AM in reply to: karlkarpuk

What software have you used before? It will help to know where you are coming from.

Surfaces can be built from a number of different sources. Points, feature/break line, corridors, grading objects. I think it would be good to search out tuturials and use the help docs to start getting a feel for civil 3d.

-Dustin
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Message 3 of 12 (465 Views)

# Re: A very basic question about surfaces

02-06-2013 05:41 AM in reply to: karlkarpuk

About the easiest way would be to draw 4 to 6 featurelines representing the top of bank and the stream channel. Then use 2 featurelines along the bank to represent the water surface. Make a surface out of each set of featurelines and get the volume between them.

Corridor modeling is the most advanced way to do something like this. You'd create an alignment and profile for the centerline of the river and apply assemblies to create the cross sections to model the river.

Most modeling of existing rivers would be done using ground Survey. Point or Points plus surface from aerials or Iliad. But I understand this is a learning exercise.

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Message 4 of 12 (453 Views)

# Re: A very basic question about surfaces

02-06-2013 06:01 AM in reply to: karlkarpuk

Basic answer: yes, you can do that.

Personally, I would use feature lines.  But as mentioned, you have options.

I also recommend the tutorials.  If you go through them all, even if irrelevant ones, you get a good overall idea of the scope of the program, and an idea of what you need to focus on afterwards.  I never had any official 'lessons', just the tutorials and a coworker who was learning the program 6 months ahead of me (but had a good LDT background).  I'm not saying don't get lessons, I'm just saying that the tutorials will help.

Credit where credit is due! Give kudos or accept as solution whenever you can.

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Message 5 of 12 (443 Views)

# Re: A very basic question about surfaces

02-06-2013 06:36 AM in reply to: karlkarpuk

See if any ot THESE help.

Valued Contributor
Posts: 56
Registered: ‎08-07-2012
Message 6 of 12 (364 Views)

# Re: A very basic question about surfaces

02-08-2013 01:06 AM in reply to: karlkarpuk

Alright! I did go throught SOME tutorials involving surfaces but there are very many and i wanted to start with simpler tasks that i made up for myself to get comfortable with those first.
I now know to take up feature lines and corridors next.

Thank you!

Mentor
Posts: 240
Registered: ‎07-19-2012
Message 7 of 12 (355 Views)

# Re: A very basic question about surfaces

02-08-2013 02:51 AM in reply to: karlkarpuk

Cheers

- Mick

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Message 8 of 12 (334 Views)

# Re: A very basic question about surfaces

02-08-2013 08:54 AM in reply to: karlkarpuk

Now to go to the far end of the scale. The attached is a Model of the bed of the Hudson River between Rockland and Westchester counties. I created it from benthic data (sidescan sonar) downloaded from our state GIS ClearingHouse. The project was to determine the Thalweg (deep channel) that marks the county boundary.

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Message 9 of 12 (329 Views)

# Re: A very basic question about surfaces

02-08-2013 08:57 AM in reply to: AllenJessup

Kudos for using the word Thalweg. That's got to be one of my favorite words!

Brian Hailey
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Message 10 of 12 (324 Views)

# Re: A very basic question about surfaces

02-08-2013 09:08 AM in reply to: AllenJessup

I didn't know it until I had to determine one. My research on boundaries turned it up. Now I even know that the original pronunciation would be Thallveg.

The real problem is trying to explain it to people who see the County Line on a map and try to say that it's wrong because the line is the "Center" of the river. I tell them to read the legal case about the ownership of Ellis Island.

The weird thing is that he boundary between New York and New Jersey is different depending if you're talking about the surface of the water or the bed of the river. On the surface it's the high water mark on the New Jersey shore. On the bed of the river it's the thalweg. The Ellis Island case hinged on the fact that most of the island is fill. You can't change a water boundary by filling. So NY has the jurisdiction on the original island that was above water while NJ has jurisdiction over the filled portion which would still be considered part of the river bed.

Why do I know these things? Because people keep ASKING!!

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