Point Clouds Civil 3D 2011

[mlohr]

Does anyone know how to see the elevations assigned to individual points in a typical point cloud? Selecting an idividual point selects the point cloud object instead. Floating your cursor over the individual points returns a preview box that has an elevation field and a value, but as you around in the point cloud, it keeps returning the same value, even when the points colored by elevation range indicate they are greatly different elevations.

I know you can create a surface from the point cloud data and then get elevation data from the surface. And I know you have several ways to display the elevations using the point cloud style, but was hoping there was a way to directly see the individual point elevations.

I am working with a cloud generated by attaching LAS files processed from  LIDAR data.

Thanks for any help.

[tcorey · Accepted solution]

Type ID at the command prompt. Snap to a Node.

If you need to do several and don't want to start the ID command over and over, type Multiple [enter] at the command line and enter ID when it asks which command to run.

[mlohr]

Sounds super easy.  I hadn't tried to use ID. I thought since it selected the entire cloud upon picking, it couldn't recognize the individual entities.

I elevations in the point cloud are in meters and I need them in feet to use with another surface to create cross sections. I looked for a way to export a group of points from the cloud to a csv file, but no luck. Any ideas on that?

Thanks for your quick response Tim. 

[Hidden_Brain]

create a tin surface from this point cloud using a metric template, then landxml the surface out and landxml back in to a fresh drawing created with an imperial template (or your project drawing if it already in imperial).

[mlohr]

Thank you Avishek. I see where this would change the meters to feet, but would it also change the Z (elevation) values associated with the point cloud points?

There is a nuance in that while C3D lets you set a horizontal datum (coordinate system) and units (meter or feet) it does not allow you (that I know of) to specify a Vertical Datum. In my part of the world, there are two datums in use (NAVD88/NGVD29) and they differ by a little over one foot in my area.In low lying tidal areas this difference can be important.

If I had a surface generated from standard C3D points, I would export the points to a CSV file and do the conversion, then import back in.  AutoDesk is lacking in the ability to manipulate the vertical elevations of 3D point data internal to the program. Or I am lacking that knowledge.

[Hidden_Brain]

Give the landxml export-import a try, i am pretty sure that it will change the vertical as well.

As for changing between NAVD88/NGVD29, you can use the AutoCAD Move command to move entities up or down as:
Move from: 0,0,0
Move to: 0,0,1 (this will move the contours up by 1 ft)

For tin surfaces, you can either use move command or a different command called RAISELOWERSURFACE.