AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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Post 1 of 18

Converting DEM surface from meters to feet

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03-24-2010 07:58 AM
I have DEM surface information that is all metric. I want to convert to imperial. I have changed the horizontal coordinate system to my local grid in feet, but I cannot figure out how to change the vertical surface from meters to feet. It should be a simple multiplication, but I cannot figure out how to perform any adjustment of the vertical elevations besides adding an offset.
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Post 2 of 18

Re: Converting DEM surface from meters to feet

03-24-2010 12:56 PM in reply to: clbreinholt
1. In drawing Toolspace
Settings > Drawing Settings > Units and Zone SETUP DRAWING COORDINATE SYSTEM ZONE AND UNITS

2.Settings > Surface Style

3.Prospector Tab
Surface > Create
Set Description
Set Style

4.Prospector Tab > Surfaces > Surface1 (+ EXPAND)
DEM > Add
Select DEM file (USGS ascii format)
Set CS Code
Set Null Elevation
OK

Note files in the DEM.SDTS.TARgz format can be converted to the USGS ascii format using MICRODEM (a free download from USNA)

Jim
MATRIX SURVEYS
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Post 3 of 18

Re: Converting DEM surface from meters to feet

03-24-2010 09:24 PM in reply to: clbreinholt
Thanks for your reply. This is a good description of how to import a DEM and convert the horizontal alignment. However, my problem is still the same. This process does not covert the vertical surface from meters to feet. The horizontal surface is correctly converted to feet, but the vertical remains in meters. BTW, the DEM I have is a GeoTIFF.
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Post 4 of 18

Re: Converting DEM surface from meters to feet

03-25-2010 06:55 AM in reply to: clbreinholt
CS (coordinate system code has to be set in lower window) DEM insert screen

DEM files are usually in UTM NAD 27 METERS need to know the Projection (NAD 27 or NAD 83) and the Zone)

Wizard only works in same projection. Have to fill in the Systems in the lower Window for a transform.

Jim
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Post 5 of 18

Re: Converting DEM surface from meters to feet

03-25-2010 09:10 AM in reply to: clbreinholt
This is interesting
When I create a new TIN surface, then set my GeoTIFF file as DEM input source, set the CS codes correctly and import, the horizontal projection is adjusted correctly, but it won't convert the vertical projection to feet. However, if I create a new Grid surface and select my GeoTIFF file as the DEM input source, I cannot select a CS code for the DEM file. I do notice that in the "DEM file information" area the coordinate system is being read from the file. When I go ahead and import the surface, the vertical is adjusted to feet, but the horizontal is not transformed.

PS
DEM files are not always in UTM NAD 27. I have to use what I have, which is Lat/Long NAD 83.
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Post 6 of 18

Re: Converting DEM surface from meters to feet

04-27-2010 01:53 PM in reply to: clbreinholt
Have you found a solution to this issue yet. I have run into the same problem, using the same data sources.
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Post 7 of 18

Re: Converting DEM surface from meters to feet

04-27-2010 03:37 PM in reply to: clbreinholt
No Autodesk solution. I found a program called Global Mapper that handles DEMs and images well, and it will convert meters to feet and change coordinate systems with little problem. It also merged and cropped my DEM. The only kicker is that it costs $350 to purchase. I haven't tried 2011 yet to see if they changed anything.
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Post 8 of 18

Re: Converting DEM surface from meters to feet

09-13-2010 08:34 PM in reply to: clbreinholt

Greetings!  In Civil3d 2011, I started to play with the point cloud to take the ddf files to create surface.  What I am curious to know is that the DEMs are in meters and I am looking to work in US feet...it would appear that if I have my drawing setup for the same zone and projection and I specify that the ddf are to be in the same format, does that mean that point clouding converts the meters into feet and places the file into the proper coordinate system?  I am not sure if I need to make any adjustments or where to begin to verify that the information is good and viable to use for preliminary project work.  Thanks!  PS I did go through the tutorial and this was not addressed. 

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Post 9 of 18

Re: Converting DEM surface from meters to feet

09-14-2010 05:43 AM in reply to: clbreinholt

I wrote a blog post on this topic a while back and I remember coming across an issue something like this. I believe the solution was to create a regular surface and add the DEM file to it. If you create a surface from a DEM file, things acted weird.

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

Brian Hailey
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Post 10 of 18

Re: Converting DEM surface from meters to feet

09-14-2010 07:08 AM in reply to: clbreinholt

just a thought, what happens when i bring in the DEM in one dwg, then insert that dwg into a new dwg as a BLOCK, with a Z scale of 3.2808?

Avishek Chhibber, P.E., CFM
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