Reducing Clipping Cropping DEM Surface

[Anonymous]

First time Civil3D user. I'm trying to put together a SIMPLE road design project for a CE453 geometric design class (data->surface->alignemnt->profile->crosssection->cut/fill->plans).

I went here (http://data.geocomm.com/catalog/US/61087/2366/group4-3.html) and downloaded the two portions of the county that where my project is located. The two tar.gzs came as a bunch of DDF files and I used this (http://data.geocomm.com/dem/sdts2dem.html) to combine the DDF files into a DEM. Since I had two sections, I ended up with two DEMs.

I opened Civil 3D and added two surfaces (created from each DEM), but I only need a small section shown in the rectangle in the picture. How can I reduce my surfaces to this area?

Also, am I even close to doing this right? I've used (unfortunately) EaglePoint and Carlson in the past. I wish I would have just learned Civil3D, but now I'm stuck Googling how to find free surface data and use this daunting 4GB program and teach it 😕

Thx for the help!

[antoniovinci]

You can add a vector boundary to the surface definition, then export the subset to a new smaller Dem.

[Neilw_05]

Read the help file about Data Clip boundaries. A data clip boundary can be added to a surface BEFORE you add any data, so unlike a normal boundary, it actually reduces the extents of the data that has to be processed.

[sfore]

I'm assuming you would have to add the data clip boundary to area of need (coordinately correct) before a .dem file was brought in....correct??

To do this, i would need to bring in a USGS quad or turn on Bing mapping via Geolocation tool to add my data clip boundary in area of need before I bring .dem file in.

[Neilw_05]

Those methods can be used to determine the extents of the clip but there are other mjethods as well (i.e. inquire a LAT/LONG or NorthEast from a web map, a parcel overlay, etc. You can also build a point cloud and display it to determine the extents of the data, then draw the clip boundary within the extents. Any method will do.

[jmiller7FCJ7]

Many many thanks!  This has saved me a lot of heartache.... 😉