Best way to compare LIDAR data to 3D surface model

[kschweizer]

I'm using 2013 Civil 3D/Map 3D.  It's my first go around at working with some LIDAR data we recieved, but it's easy enough to bring it in as a point cloud and from there convert it to a 3D raster or Civil 3D surface.  What I'm getting hung up on is I need to compare this data to a design 3D surface model (vertically) and extract the points that are above it.  Is there an easy way to do this with Map?  There's nothing in the Help section and I've searched the forum but haven't come across anything.

Thanks,
Kyle

[Alfred.NESWADBA]

Hi,

>> Is there an easy way to do this with Map?

As you have Civil 3D why do you want to use Map 3D therefor? I would create two Civil 3D surfaces from your data, then create a volume surface from them (to get the difference). In that volume surface you can now filter to the points Z > 0.0 ==> these points are the ones for surface 1 (Z) > surface 2 (Z).

HTH, - alfred -

[kschweizer]

Thanks Alfred,

That was my first thought, but the problem is it only gives me a cut/fill surface where the elevations are the differences between the two.  Here's a screen shot from a test file I'm  experimenting with showing what I mean.  The volume surface is below, starting at z=0.  I need a way to extract or clip the data inside the surface, whether it be part of a point cloud, surface, or cogo points.

[Alfred.NESWADBA]

Hi,

>> I need a way to extract or clip the data inside the surface

In your volume surface activate one contour at level Z=0 (that is the border between lower and upper area or with other words where one surface dives into the other), extract that contour and use this new polyline as inner border on your master surface.

Hope that short wording is understandable, - alfred -