AutoCAD Civil 3D

[#1]

I downloaded a digital elevation model (dem) to practice my C3D skills on. I have an acount with GeoCommunity. The file is 1693201.DEM.SDTS.TAR.GZ that is idenfidied as a WinZip file. It is for the county where I do most of my work. When unzipped did not contain anything with the dem extension, all the files have a ddf extension. How can I add it to my drawing since it will not show up under DEM Files in the Toolspace? There is a rather complicated procedure to convert SDTS DEM files to ASCII  XYZ files but I'm not sure i need to do that.

If I downloaded the wrong type of file is there a source of free DEM's or other GIS data?

[#2 · Accepted solution]

You'll need to convert the SDTS to DEM - but it's very simple. Just go to this website and take a look, and you're good to go!

[#3 · Accepted solution]

if you have a .sdts file, there is an old DOS routine SDTS2DEM.EXE that will convert the file to a usable dem fairly painlessly.

1, you need to open up on of the files to determine the name you want.

2 run from "CMD" command line - drag& drop sdts2dem.exe into your folder with the sdts files.

enter first 4 digits of the series of sdts files

enter the output file name.

from create surface in C3D, you'll have to manually enter the dem coordinate system designation, but it's not too hard - albeit could be easier...

best of luck,

TdH

[#4]

Thank you Jason. I used SDTS2DEM years ago when the autocad I had didn't know what to do with it. I downloaded the newer version and now have a DEM surface to analize.

[#5 · Accepted solution]

as a followup  - from my experience....

create a blank TIN surface first, not a DEM surface

once you create the tin surface, then select "add dem data"

select your file -

once it recognizes your file & shows you the dem coordinates, then add that to the section in the bottom portion of the dialog box to state "UTM27-13" or whatever it is.

then you should get a dem that is in FT versus elevations in meters....

[#6]

Thanks thepworth. I'm using C3D 2010 and created the surface from DEM in Toolspace. I'll work on creating another smaller surface from it and making a drawing containing contours etc. Right now the contours are all on one layer but the index conturs are a darker color. At least this is a start.

[#7]

as a pps...

i go to "mapmart.com" for free data, versus the geocommunities website.  mapmart has all of the 10m/30m usgs dems per quad map for free in sdts format or they'll charge $5/quad min $15/order for converting it over to dem or providing a dwg of contours for you....

best of luck

Todd

[#8]

Thanks. I'll try mapmart. One more question- Is it possible to get roads, houses, vegetation, streams in addition to the elevations?

[#9]

that's more of a DLG (digital line graph) versus DRG (digital raster graphic)

roads, water/streams/river/rails available from us census TIGER data...

look for "edges of census blocks" - then you need to stylize based on 'hydroflg="Y"' for water, "Roadflg='Y' for roads, etc.

not much out there for tutorials, kinda had to learn this on the fly...

[#10]

Sorry for the late, gentlemen.

If you have a .GZ dem file, you DON'T need to unpack it, definetely.

Open it directly to view all its beauty with this tool:

 

then FILE -> save as "USGS Ascii DEM" to get a fully Acad compatible stuff.