AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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Active Member
allysonduncan88
Posts: 6
Registered: ‎10-02-2012
Message 1 of 10 (2,561 Views)

DEM Import for AutoCAD Civil 3D 2012

2561 Views, 9 Replies
10-02-2012 08:40 AM

 

I am issues with DEM files that I am downloading from the USGS website.

 

I download 24k, elevation for the area I need. I then choose staged 1 second, add a surface to a blank drawing, then upload the DEM files to the surface.

 

The surface imports correcty, but when I try to import  points taken by a surveyor on the same drawing, they plot incorrectly.The DEM surface and the points from the surveyor do not correspond. Also, the DEM surface is in meters, not feet.

 

What am I doing wrong? I have tried changing drawing settings, datum types, coordinate types, etc.

 

Thanks!

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AllenJessup
Posts: 5,914
Registered: ‎05-21-2003
Message 2 of 10 (2,557 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 08:49 AM in reply to: allysonduncan88

Look at the Metadata regarding the DEM to confirm that it is in the system you expect. Then verify the system and datum of the survey data and how it was determined. After you've confirmed that and it still doesn't work should you look for errors in the software or your procedures.

 

You say the datum is in meters. Are the survey points also in meters?

 

Allen

Active Member
allysonduncan88
Posts: 6
Registered: ‎10-02-2012
Message 3 of 10 (2,551 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 09:11 AM in reply to: AllenJessup

I will check into this, thanks for your quick response. My theory was that the survey points need to be converted to correspond with the DEM data, but that still doesn't explain why the datum imports in meters when I specify feet when setting up the drawing.

 

The survey data imports in feet.

 

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AllenJessup
Posts: 5,914
Registered: ‎05-21-2003
Message 4 of 10 (2,545 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 09:34 AM in reply to: allysonduncan88

I don't work with DEMs much. It looks like you have to enter the information on the DEM manually. At least in the test I did. Hopefully the survey points are in a defined system, not a local one. If they're not in a defined system the only way to "convert" them to the system you import the DEM in would be by eyeball. Hopefully things will look better when you get the DEM in in Feet.

 

Allen

 

Actualy it looks like I had the first try wrong. I think this one is better. Also: make sure whether you need to import as International Feet or US Survey Feet.

 

dem2.PNG

Active Contributor
jamesmac1200
Posts: 47
Registered: ‎04-23-2010
Message 5 of 10 (2,530 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 12:30 PM in reply to: AllenJessup

Here is the problem I am having. Here are the steps I took:

1)  Assigned a coordinate system to the drawing

2)  I created a new TIN surface

3)  I added the DEM surface from the Prospector (Surface - Definition - DEM files)

Here is the problem:

4)  (see attached) attempted to change the coordinate system of the DEM but unable to do so.

 

Any suggestions? Thanks in advance.

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AllenJessup
Posts: 5,914
Registered: ‎05-21-2003
Message 6 of 10 (2,526 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 01:01 PM in reply to: jamesmac1200

If you click in the field twice, you should get the ellipsis button.

 

Allen

 

dem3.png

Active Contributor
jamesmac1200
Posts: 47
Registered: ‎04-23-2010
Message 7 of 10 (2,517 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 01:19 PM in reply to: AllenJessup

Thanks for the quick response. Unfortunately that didn't work. I know what I did wrong. I didn't add the coordinate system when I initially added the DEM file. When I went into the properties to add the coordinate system later, I didn't have the option to do so. So to whomever read this, make sure to add the DEM coordinate system with the DEM file at the same time. Otherwise your DEM surface will come in some random location and size :smileyhappy:

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BrianHailey
Posts: 2,815
Registered: ‎04-27-2005
Message 8 of 10 (2,504 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 02:52 PM in reply to: jamesmac1200

If you have the infrastructure design suite, import the DEM file into Autodesk Infrastructure Modeler and then export it as a .imx file. Bring that into C3D.

 

Haven't really tried it but it "should" work.

Brian Hailey
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BrianHailey
Posts: 2,815
Registered: ‎04-27-2005
Message 9 of 10 (2,503 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-02-2012 02:53 PM in reply to: allysonduncan88

For some help with bringing DEM files directly into C3D, see this post I did a while back:

http://civil3dplus.wordpress.com/2010/02/02/using-dem-information-in-civil-3d/ 

Brian Hailey
CAD-1.com
My Blog
Active Contributor
jamesmac1200
Posts: 47
Registered: ‎04-23-2010
Message 10 of 10 (2,464 Views)

Re: DEM Import for AutoCAD Civil 3D 2012

10-03-2012 07:32 PM in reply to: BrianHailey

Just FYI, that post is great. I printed it and placed it in my continuity folder (also saved as my favorites)

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