DEM Surface Incorrect Location

[Anonymous]

I was tasked with trying out C3D 2021 because the company license is renewing at the end of the month and we'll be losing the use of C3D 2017. One of the major workflows is to import lidar data and create a surface. I was able to complete that workflow and create a surface by processing the lidar data in Recap but C3D will not allow the data to be filtered by classification so its not possible to use only ground data.

I used the "MAPCREATEPCSURFACE" command that will allow the data to be filtered out by classification and created a DEM and plan to use that to create a surface. The problem is that when I create the surface from the DEM it doesn't populate at the correct location. The DEM is in the correct location but the surface doesn't drop on the DEM but is approximately 1,400 miles Northwest. I have tried several things but am not able to figure out why the surface doesn't overlay in the same location as the DEM. Any Ideas?

[Pointdump]

Kevin,
You can use either LAStools or CloudCompare to filter Ground-Only Points before bringing it in to ReCap. Good workflow >>>Here<<< and >>>Here<<<.
For the problem with the DEM, please post the DEM. (You might have to Zip it for the Forum to accept.)
Dave

[Anonymous]

Thank you for the response. I did like the surface created using the cloud compare method but seem to have issues with cloud compare. I was able to use it once and then it will not open again so I uninstalled and reinstalled and still no luck. My company anitvirus will not allow the download of LAStools so I wasn't able to perform that work flow. Still upset with Autodesk for removing the filter classified points function.

Attached is the dwg where a DEM was created with a recap point cloud and a surface created from the DEM. As you can see the DEM lays directly on the point cloud but the surface doesn't lay on the DEM. Any ideas would be appreciated.

[Pointdump]

Kevin,
I wasn't able to do much. Drawing needs the MMS file to recreate the surface and the Tiff doesn't seem to have any metadata in the header, so Civil 3D(and QGIS too) can't figure out what to do with it.
Where did you get the point cloud that made the original surface?
Another option for bringing a point cloud into Civil 3D is to use >>>DotSoft LiDAR Tools<<<.
Dave

[jefflambert9091 · Accepted solution]

I suffered for awhile going through recap. I did not watch the vids linked in this post, but I do remember that you may have to set your drawing units to US foot when bringing in from recap. I found the DotSoft Lidar Tools to be a good and much easier solution.  We now use it companywide. 

[ChicagoLooper]

Here's an experiment:

Make the DEM use coordinate system UTM83-6 meters? DEMs like meters, not State Plane, and not feet. (Don't give the DEM a State Plane georeference.)

It's perfectly OK to assign a UTM coordinate system to the DEM then use State Plane in modelspace because C3D will perform a coordinate TRANSFORMATION from one coordinate system to another. You simply need to tell C3D: (a) This DEM is using UTM83-6 meters and (b) Modelspace is using State Plane AK83-4F. Will C3D perform the TRANSFORMATION? Try it and find out.

1. Go to Toolspace=>Create a New. Give it a name (EG)  and a surface style (50' and 250').
2. Expand Defiinition=>DEM=>Add 
3. DEM browse button=>DEM File=>CS Code=>UTM83-6 meters (Step 3 is vital.)
4. Confirm that Current Drawing=>CS Code=>AK83-4F
5. Click OK. Turn on Bing Aerial imagery. 

(This won't work on the current DEM, the current DEM is not good. You need to create a New one with UTM georefereence.)