Surfaces in Civil 3D with USDA Data

Hello Civil 3D Users,
Do you need to create/generate surfaces for large areas?  Here is a way to Import USDA GeoTIFF’s into Civil 3D – (Areas are approx. the size of USGS 7.5 min Quad):

1.       Go to https://gdg.sc.egov.usda.gov/

2.       Once on the home page click the GET DATA button (Green circular button).

3.       Select a State, then select your County.  Then click on the “Submit Selected Counties” button at the bottom of the page.

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4.       Next browse down the list and look for Elevation.  Then select your Elevation Dataset.  I am selecting 10m here.  If three meter (3m) is available then that is preferred.  Three meter files will also be bigger in size.  Once selected, then scroll to the bottom of the page and click on the CONTINUE Button.

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5.       Review to make sure everything is correct, then select CONTINUE.

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6.       Next, fill in all the pertinent information.  Then select CONTINUE.

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7.       Review and the select PLACE ORDER.

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8.       Once you place the order you should get an email in about 15 to 30 min. stating your order is ready to be downloaded.

9.       Once downloaded unzip the file and extract all of your Geo Tiffs and other associated files.

10.       You should now have 4 files for each Tile.  One Tile being one 7.5 min quad (approx..).  I believe Civil 3D only uses the *.tif and *.tfw files for import.  The ned documents.html  file is where the data was derived from.   The ned_FileNaming.txt file explains how their grid system and naming of files is set up.

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11.       Start Civil 3D with Your DWT Template (US Survey Foot).

12.       Assign your Coordinate System to the drawing.  Go to Settings Tab in Toolspace > right click on the drawing name > Edit Drawing Settings > Units and Zone Tab.  In my case, I will assign Colorado State Plane, Central Zone, Feet.  The Coordinate System code is CO83-CF.  An alternative is to use the MAPCSASSIGN command, typed in at the command line.  This is a Map 3D command.

13.       Next go to Prospector Tab in Toolspace > rt clk on Surfaces and Create a new Surface.

14.       When greeted with the Create Surface Dialog box make sure the Type is set to TIN Surface, then Pick the Surface Style of your choice.  (Warning: 1 foot contours are probably not advisable)

15.       Once the Surface has been created expand Definitions, under that look for “DEM Files”.  right click on that then select Add…

16.       Once you get the “Add DEM File” dialog box, In the upper right hand corner select the Surface Symbol and browse to your *.tif file. Make sure you change the files of type to *.tif.   Do not mistake this file for an image, it’s what’s called a Geo-Tiff.

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17.       This is your Geo-Tiff’s source coordinate information.   NOTE: USDA and USGS data will always be in UTM zones, primarily meter.  In order for C3D to re-project this into Feet we need the source information.  In this case the source coordinate system is UTM83-13.

18.       In this area you specify the Source file’s coordinate system information.  Click on the Value column CS Code row.  Once you click in there you will get an ellipses.  Click on the Ellipses and specify the coordinate system code.

19.       Right below the DEM File information. should be the current drawing coordinate system.  See note 12 from above.

20.       Once you click OK let it process for a minute or so and you should have a surface.

21.       Confirm that Civil 3D has Translated from UTM83-13 zone to Colorado State Plane Zone, or whatever zone you picked in Step 12.

22.       Confirm that the Elevations are in Feet and NOT in Meters.


I hope these instructions help the next time you need to create/generate surfaces for large areas!

 

Until next time,

 

Ken Martinez, ACI

Civil/Survey/GIS Technical Specialist.

kenm@ctcivil.com

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