Contour Lines don't match Surveyors Contours

[tknapp]

Here is the situation. We have aquired a CSV file that we want to import inot Revit for our surface. We we import the points & the surface is created, the contours look nothing like the contour lines that were provided by the surveyor. Why is this? The previous contours were laid out on 2'-0" increments. If we change our contours to 2'-0" increments, it still looks nothing like the surveyors drawing. Are we doing something wrong?

[cdatechguy]

I got a CSV file from someone last week and I had to remove the point numbers....then the point labels...and then reverse the X,Y columns...

Some programs will export as #,Y,X,Z,Note....your best bet is to just get X,Y,Z....

Edit the point file to reverse the X,Y or Y,X and see if that works..

[Alex Page]

can you provide scrrenshots of surveryers contours andyours?

[d.stairmand]

Also remember that the Contour Lines are the Civil's Program Interpretation of the points. Revit may interpret the points differently.

If all else fails - Use the points!

[tknapp]

I got a CSV file from someone last week and I had to remove the point numbers....then the point labels...and then reverse the X,Y columns...

Some programs will export as #,Y,X,Z,Note....your best bet is to just get X,Y,Z....

Edit the point file to reverse the X,Y or Y,X and see if that works..

Thanks for the advice. I had already removed the point #s & correcte the X,Y & Z order.

I will try to post some screen shots soon. I am just not sure that I can validate the information.

[David Conant]

This is a result of the way that Revit creates contour lines. In Revit, the application builds a triangulated surface from the points supplied either as CSV points or Pline nodes. Once that surface is created, contour lines are generated by intersecting it with planes at each contour interval. Thus, the contours are a result of the surface form and not the generator of the form. Since the form is composed of triangular facets, the contour lines are always composed of a chain of straight segments (not splines).
In traditional site plans with contours, the contour lines are an indication of where the surface should be. They are drawn as smooth splined curves and do not have to conform to any actual surface in the digital model as surfaces are not usually modeled in a 2d site plan. In effect, the contour line surves as a substitute for the surface.
Because of the differences in method, Revit contour lines will never precisely match those in a site plan. Increasing the number of points used to generate the Revit surface may bring them closer together, but there will likely always be some differences. These will be particularly noticeable where the site is relatively level at one of the contour intervals. There, slight differences in surface height due to triangulation can push the surface above or below the contour interval and generate large changes in the contour line position.