![]() Likewise the units for most DEM’s will be meters. Most DEM’s you download from the Geo Community will use a UTM with NAD27 datum. Look at the information listed under DEM file information to discern your source coordinate system.Click on the button for CS Code under the DEM file tree node.With our DEM file teed up, we now need to tell Civil 3D how to project the DEM surface to my current coordinate system.Use the button to browse to your DEM file from the Add DEM File dialog.Right-click on the DEM Files node and select Add… Plus out your new surface in Prospector and navigate to the Definition>DEM Files node.Note: I prefer naming my surface something like EG-DEM to make it’s origin very obvious to other team members. Define your surface by giving it a name, assigning it’s style, etc.Right-click on the Surfaces node within Prospector, and select Create Surface.Settings tab, right-click / Edit Drawing Settings, Units and Zone tab. Make sure the correct coordinate system is assigned to your drawing.Creating a Civil 3D DEM Surface Definition DEM file that can be used to build a surface in Civil 3D. While you can name this anything you want, it’s recommended you name it after the Quad name.Īfter completing step 5, you will now have a. Next you’ll be prompted to enter the output file name.This is the first 4 characters of the DDF files, not the initial TAR.GZ file. Upon running the program you will be prompted to enter the first 4 characters of the SDTS file name.Accept any security prompts that may appear upon running the program. Double-click the sdts2dem.exe file to run the executable.Place the sdts2dem.exe file in the same directory as the data you extracted above.It’s just a small console application that will produce the DEM file necessary for Civil 3D. This is done using yet another free download named sdts2dem.exe. Compiling into a Importable DEM Fileīefore we can use the surface in Civil 3D we must first compile it into a single DEM file. Civil 3D cannot read a DDF file, and therefore must be compiled into a DEM file. We’ll use the same process to extract the. TAR file which also needs to be extracted. Depending on your files location you may choose to use one of the other extraction options. Note: I placed the file in an empty directory. ![]() Right-Click on the TAR.GZ file and select “ Extract Here”.Navigate to the file using Windows Explorer (My Computer).While there’s an endless list of programs that can do this, I prefer 7-Zip (Free Download). To get the DEM we must first unpack the file. This is a compressed file format similar to a ZIP file. Note: You downloading from the Geo Community does require you to create an account (Free)ĭownloads from the Geo Community website are provided as a TAR.GZ file. Click the green download button for the necessary Quad.From the county page, select “ Digital Elevation Model (DEM) – 24K”.Find the county from within the state you selected.Using the map, click on the state your site is located in.Go to the Geo Community DEM download page:.To download a DEM you will need to know each of these (state, county, and quad name) The Geo Community DEM’s are organized first by state, then by county, and finally by quad name. Now don’t be fooled when you visit the site as you will see all sorts of premium content never fear as there’s ample data that can be had for free! ![]() The great thing about DEM’s is they’re readily available for FREE from a wonderful website named the Geo Community. This is fundamentally different than DTM’s (standard Civil 3D surface) which still stores a collection of points, but in the form of triangles not a structured grid. For the uninitiated, DEM’s or Digital Elevation Models could be described as a surface whose data is organized in a grid. ![]() While importing surface data from Google Earth is probably the easiest way to get some conceptual topographical data into your drawings, DEM’s have to be a close second.
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