How to create a design surface

In order to create a more accurate design surface in Civil 3D, the point cloud used to create the surface must be cleaned of all points that aren’t “ground”. Autodesk’s Infraworks software has a brand new tool to automate the cleaning of point clouds generated by Site Scan.

First, create a new Infraworks model. You can either use their “Model Builder” which pulls public data (streets, elevations, buildings) from the internet and builds a basic project automatically, or you can create a new empty project and add data yourself. For simplicity, I’m creating a new empty model.

Give the model a name and extent. If you don’t know the extent of your project, you can use the orthomosaic to add the extent automatically.

Once the empty project has been created, import your RCP file. The RCP file is generated when opening an RCS or LAS Point Cloud in Recap 360, or it can be found on your A360 drive.

  1. If you have created an RCP in ReCap 360 using the LAS file, the point cloud will be georeferenced and drop into the correct location automatically. (Preferred)
  2. If you are using the RCS file generated from Site Scan, the point cloud will have to be placed by inputting the project coordinates. Instructions on how to do this step can be found here:

After the point cloud has been imported, navigate inside the orange Infraworks menu, and find the tool “Point Cloud Terrain”.

This tool will ask you which point cloud to use, some processing rules, and results options. You will want to export “All Points”, the processed file should include “Only ground points” and the save file should be set to a location you can find later. Once these options are set, click “Start Processing”.

The processing will take a few minutes, depending on your computer specs.

Once the processing is complete, in the folder location specified earlier, you will find a new folder that contains the new cleaned point cloud.

You can now import this RCS file straight into Civil 3D. Notice how all the buildings and fences in the subdivision are now gone!

Now you can create a Civil 3D surface using the cleaned point cloud. One important step is to change the “Distance between points”. The default value will be very small, and will result in a surface with tiny triangles. Increase this number to a more reasonable value in order to reduce the number of points to about 3 Million or less. I selected 0.3 units, which in this case is meters, which amounts to about a foot between points, and selected just over 1 Million points.  

Next, to ignore some of the non-ground points that Infraworks might have missed, select “Kriging interpolation”. For faster processing, use “No Filter”.

After clicking “Create Surface”, Civil 3D will work in the background to create the surface.

After the surface creation is complete, the result should be a nice smooth surface of only the points on the ground.