Forums >> Revit Building >> Technical Support >> matching contour lines from civil CAD when creating Topography (2019)

ledgewood33

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Joined: Wed, Jan 27, 2010
34 Posts

is there a way or method to match contour lines from civil CAD when creating Topography? after creating the topography from the the civil CAD it seems that most of the time the contour lines do not match the original civil survey from the CAD that I imported to revit. i overlay the civil CAD and the contours that seem to not line up tend to be the swale's. therefore, i am going back into the edit mode of the topo to place points so that the contours in the revit topography match the civil CAD survey.

any suggestions?

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WWHub

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Joined: Tue, May 16, 2006
19889 Posts

I would have thought you may have seen my posts on this subject before but here it is again.  If you started out hand drafting, you would know this.

Contour lines should never be thought of as being precise.  If you want precise, then use spot elevations that have been produced from a survy.  Contour lines are ONLY a visual representation of the topography.

When hand drafting, the surveyor typically takes spot elevations on a grid he lays out along with special, unique spots that are identified off the grid.  When the draftsman creats a contour line, he draws his line at a VISUAL point that works with those spots.  So say he is creating contours at 5' intervals and at quadrant 10/10 the spot elev is 101.95 and at quadrant 10/20 (obviously 10' grid) the spot elevation is 106.43.  Well, the only line that goes between those two spots is 105 so he interpolates and draws that somewhere nearer the 10/20 grid.

Hand drafting is all visual ... you don't do any math.  The computer does the same thing except it uses math and follows its own program (not all are the same).  But it does not connect these grid intersections with straight lines.  It uses a polyline that is flexed to create gentle curves.

TThe final word:  DON'T GET HUNG UP ON ONE TOPO NOT EXACTLY MATCHING ANOTHER that was created elsewhere.  Revit's topo's are good quality and they reflect the imported spot elevation data.

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