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Im am trying to export my contours from ArcMap to AutoCad from a .tiff. I am able to get the contours extracted and opened in AutoCad but they come out flat. I made sure I was inserting the correct 'contour interval' when extracting contours from the raster but they still come out flat. Can any one please help out?

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  • Are your contours a 3d feature class? I was fairly sure that if environment setting 'output has z values' was set to enabled the outputs would have their heights assigned... not 100% certain though, it could have been another contour utility. If not GDAL_Contour with -3d option will create 3d shape files gdal.org/gdal_contour.html. Apr 14, 2015 at 5:45
  • I have converted it to a tin and still there is no z value attributed when I look in the files properties. I have exported to CAD before but the contours were already formated for me Apr 14, 2015 at 21:40
  • When exporting to CAD with ArcMap the elevation is an attribute that can be copied: 2d Shape with Elevation to 3d DXF; the 3rd party software endorsed by FelixIP should (could) do the job but I can't say for sure having not used it. I don't work much with CAD (if I can help it). Can you explain more about your CAD conversion and the tool(s) you use? Perhaps there's a switch that needs to be set. Apr 14, 2015 at 21:55
  • here are the files Im using dropbox.com/sh/untszm39yfeqere/AADrQjPLyyRWSD-Vb25VKcjCa?dl=0. As you can see they are flat before evening using the 'export to CAD' tool. Apr 14, 2015 at 22:02
  • I can't access Dropbox due to I.T. policy. Have you used Add CAD fields resources.arcgis.com/en/help/main/10.2/index.html#/… on the shape? This tool gives you all the fields that Export to CAD resources.arcgis.com/en/help/main/10.2/index.html#/… is looking for, this gives you an opportunity to copy the height of the contours into the elevation field, then use a 3d CAD seed file to ensure the output is 3d. Apr 14, 2015 at 22:16

2 Answers 2

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To convert 2d contours into 3d use OGR2OGR with a few switches:

-dim 3 -zfield Z_Field_Name

Example: In this case the field with the elevations is called 'Altitude'

ogr2ogr D:\SomePath\Output3d_ogr.shp D:\SomePath\Input2d.shp -dim 3 -zfield Altitude

Or even better still, directly to DXF with OGR2OGR:

ogr2ogr -f DXF D:\SomePath\Output3d.DXF D:\SomePath\Input2d.shp -dim 3 -zfield Altitude

Input (Esri) contours, clearly 2d data:

2d contour description in ArcCatalog

Output (OGR) contours, have been converted to 3d shape:

3d contour description in ArcCatalog

And in ArcScene: Both contours in ArcScene

The 2d contours (black) are flat and the 3d contours from OGR are neatly above them. I only hope your export tool uses the 3d geometry to create a 3d CAD file, if you have troubles I know OGR2OGR -f DXF will convert to a 3d DXF.

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ArcGIS does not transfer Z attribute when exporting to CAD. Seek 3rd party software, something like arc2cad.

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