topic Exporting a surface as DEM in US survey feet in Civil 3D Forum

Exporting a surface as DEM in US survey feet

Anonymous — Thu, 17 May 2018 17:18:56 GMT

Hi,

I am trying to export a couple surfaces from my drawing to a DEM file, when I go to choose the NAD 83 coordinate system for the export file, it defaults to meters.

I want to Export my DEM file in US Survey feet in the NAD 83 Montana coordinate system.

Any ideas?

Thanks.

Re: Exporting a surface as DEM in US survey feet

dbinkney — Thu, 17 May 2018 20:20:08 GMT

Aloha,

Check out the link below, where I found this quote:

"the DEM format only accepts metric coordinate systems"

https://thecadgeek.com/blog/2008/06/creating-a-dem-with-civil-3d/#comments

The end user can import it and transform the surface back to imperial units however - there are several posts on that topic. Out of curiosity, why DEM export, not XML?

Re: Exporting a surface as DEM in US survey feet

TerryDotson — Thu, 17 May 2018 21:23:28 GMT

Don't even consider exporting to an actual .DEM file as it is integer meter based. You are essentially rounding off your elevation values to the nearest meter. Use the ESRI ASC Grid, GeoTiff, or other options.

Re: Exporting a surface as DEM in US survey feet

Anonymous — Thu, 17 May 2018 22:14:34 GMT

Thank you, that answers my question. As far as using a DEM, the client specifically requested it. Good information to know however, I will pass it along.

Re: Exporting a surface as DEM in US survey feet

TerryDotson — Thu, 17 May 2018 23:14:56 GMT

Your surface could likely be exported to a lidar LAZ points file and projected to US Survey Foot. Consider posting the drawing with the surface? It's assumed the DWG will already be assigned a coordinate system, then we would only need to know the target system name.