Forums >> Revit Structure >> Technical Support >> Revit Topography doesnt follow CAD import

Tellis

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Joined: Tue, May 24, 2011
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Hey,

apologies if this is the incorrect section to post this but it seemed ok when i looked at the other topics.

I have a block of land we are developing for a University project, it was created in CAD and a single elevation was set as we wanted the block to be flat.

i followed these instructions on how to do it:

http://bim.wikispaces.com/file/view/Landiak+BIMWiki_Creating+Topography+from+CAD.pdf

but when i finish mine, the topography surface doesnt follow the block, insted of following the curve around, it just creates a straight line which skips all the points.

iv attached a file, so hopefully it works, but i want the area to only follow the highlighted blue line which was the imported file, not the grey section that is outside of the line.

can anyone offer some assistance please, iv searched google and spent an entire day attempting to solve it but so far nothing

thanks

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Tellis

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Joined: Tue, May 24, 2011
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ok so it appears the attachment diddnt work, heres a photobucket link

http://i122.photobucket.com/albums/o241/trommie/revit.jpg

thanks

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WWHub

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Joined: Tue, May 16, 2006
13079 Posts

It will take you awhile to understand Revit's site import process. 

First thing you should learn is that Revit's contours will not usually be the same as the CAD contours.  This doesn't mean anything as far as the site goes.  Countor lines are really arbitrary and any two drafters might draw them differently in some areas. 

Revit has rules on how to interpret and triangulate the site between points.  The more points provided, the closer Revit's site might look like the CAD import.  So for a typical polyline CAD site, the points provided are at the nodes on the polyline and nothing inbetween.  Thus Revit might interpret and draw the contour lines differently.  HOWEVER, the model will have the correct elevation at each of these points.

So, if you need to adjust the site because the CAD drawing was not adequate, then just add more points.

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mbsteve

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Joined: Fri, Sep 22, 2006
759 Posts

WW's comments are right on. The "CAD" drawing which you are comparing the revit drawing to is not necessarily correct either. However, that said, the contour lines are very specific and if you think that the "CAD" drawing is more accurate than the Revit one ( I don't ) then you can manipulate the surface to move the contour lines to more closely match the lines on your cad drawing. I am an engineer, and have had some experience with the situation you are describing and if you are required by a superior to match the contours or you feel compelled to match the "CAD" drawing then what I do is set a point elevations just below and above in elevation of the contour in question and then you can move it to adjust the contour line.

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