AutoCAD Civil 3D General Discussion

Reply
Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 1 of 14 (767 Views)

Export to DEM

767 Views, 13 Replies
02-21-2013 01:04 PM

Export to DEM Issues...

 

Anybody have any experience using the export to DEM functionality for surfaces?

My understanding is that it is supposed to use USGS dem format, but I'm having trouble getting the resulting dem to show up intact in ArcGis. The extents are off and it chopped off the northern half of the site...?

 

I think this is a Coordinate System issue, but can't figure out where I can change anything...

 

two screenshots attached. one shows surface in CAD, the other in GIS.

 

Thanks!

 

-d

*Expert Elite*
antoniovinci
Posts: 1,603
Registered: ‎06-03-2011
Message 2 of 14 (761 Views)

Re: Export to DEM

02-21-2013 01:13 PM in reply to: eladkcem

What happens if you load that .DEM back in Civil, how does it appear?

Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 3 of 14 (754 Views)

Re: Export to DEM

02-21-2013 01:24 PM in reply to: antoniovinci

Hiya Antonio,

 

Thanks - I just tried that. Importing the DEM back into CAD does bring in the entire surface...

 

Hm. Any idea how well CAD has implemented the dem format? Maybe CAD can handle it, but arcGIS can't?

 

-d

*Expert Elite*
antoniovinci
Posts: 1,603
Registered: ‎06-03-2011
Message 4 of 14 (747 Views)

Re: Export to DEM

02-21-2013 01:35 PM in reply to: eladkcem

In your Civil may you export only to .DEM format, or others like .ASC or Geotiff ?

Seems like Arcgis can't decode well the .DEM one, so give a different try.

If it doesn't work, zip and attach it here, thx.

Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 5 of 14 (743 Views)

Re: Export to DEM

02-21-2013 01:42 PM in reply to: antoniovinci

Oooohhhh  geoTiff.  I don't know what that is... but yes I can and it looks great when I pull it into GIS. Thanks Antonio!

Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 6 of 14 (707 Views)

Re: Export to DEM

02-22-2013 01:42 PM in reply to: antoniovinci

So... the geotiff only kinda worked. I can view and manipulate the exported geotiff image in GIS (ArcGis 9.3.1) which is helpful.

 

However, see attached screen shot for error/warning message received.

 

My drawing is in CA state plane and my exported geotiff is also in Ca state plane so there shouldn't have been any transformation issues... thoughts?

 

Has anybody ever successfully created a dem or geotiff that ends up with a CS that GIS recognizes?

 

thanks

 

-d

Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 7 of 14 (688 Views)

Re: Export to DEM

02-22-2013 02:06 PM in reply to: eladkcem

Okay... get this. It works if I change the coordinate system of my drawing to CA state plane in meters (I was in feet earlier)...

 

Good to know... irritating, but as I've heard on this board before... there is always a work-around...

 

Hm.. I wonder if this fixes the originial issue I had with the export to dem command...

 

 -d

Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 8 of 14 (668 Views)

Re: Export to DEM

02-22-2013 03:51 PM in reply to: eladkcem

Still stuck on this. I can't get a dem (or a geoTiff) with the correct georeferencing.

 

so far the Export to DEM chops the surface weird (and produces weird errors in GIS) (My Original problem)

The geoTiff was promising.. but produces the error I linked to earlier.

If you change the CS in the dwg to State Plane meters, then GIS does not produce an error, BUT the surface is shifted (translated several meters to the west). screen shot attached shows original dem, and cad export.

 

This does not seem to be fixed even if I switch between survey feet or international feet . I've tried as many combinations of CS's, units, conversion factors, etc... to no avail... anybody?

 

Thanks!

 

-d

 

I checked all my surface definitions to make sure I didn't accidentally move the surface to the west at some point...nope! This shift is occuring for different projects with different surfaces...

Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 9 of 14 (625 Views)

Re: Export to DEM

02-25-2013 07:28 AM in reply to: eladkcem

I read through some of the older posts on this dem export issue... sems like this has been an issue since 2009!

Has anybody figured out how to get AutoCAD to export a correctly referenced and intact dem or geotiff surface?

 

-d

Valued Contributor
eladkcem
Posts: 67
Registered: ‎05-22-2007
Message 10 of 14 (611 Views)

Re: Export to DEM

02-25-2013 12:28 PM in reply to: eladkcem

I'll figure this out yet...

 

The translational error depends on the distance from the origin. The attached images show two identical surfaces (as yellow borders) except that one is located near the origin and the other is way off to the northeast (coordinates of roughly 900,000,300,000 which are not unreasonable in a state plane coordinate system). With each surface I used the autocad command export to DEM and selected the geoTiff format. I then immediately created another surface from the exported gtif... Theses surfaces are shown as red borders. They are 'blocky' as you would expect with a DEM, but note the translational shift towards the origin... Is this a precision issue in CAD or a coordinate issue? projection issue? I could use some wisdom form the board on this.... I'm not sure where I need to look next for a solution to this...

 

thanks y'all.

 

-dale

 

 

 

You are not logged in.

Log into access your profile, ask and answer questions, share ideas and more. Haven't signed up yet? Register

Announcements
Are you familiar with the Autodesk Expert Elites? The Expert Elite program is made up of customers that help other customers by sharing knowledge and exemplifying an engaging style of collaboration. To learn more, please visit our Expert Elite website.

Need installation help?

Start with some of our most frequented solutions to get help installing your software.

Ask the Community


Civil 3D Exchange Apps

Created by the community for the community, Autodesk Exchange Apps for AutoCAD Civil 3D helps you achieve greater speed, accuracy, and automation from concept to manufacturing.

Connect with Civil 3D

Twitter

Facebook

Blogs