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Tip #132: The Sample Point Cloud Region Command

By Erin Johnson posted 12-18-2020 09:03

  

Good morning TBC’ers! Have you ever been working with a very dense point cloud - collected from an MX9 scanner for instance - and wished there was a way to speed up the generation of a surface? Or have you ever wanted to eliminate points from tires on a road prior to creating a surface? Well, today I will be showing you the Sample Point Cloud Region command. The Sample Point Cloud Region command performs either random or spatial sampling on an entire point cloud region or a selection of scan points in your project to create a new sampled region for creating surfaces, exporting data, and so on. The Sample Point Cloud Region command allows us to downsample a point cloud, and thus speed up surface creation.

   

To access the Sample Point Cloud Region command, follow these steps:

   

1. Navigate to the Point Clouds Ribbon, and select Sample Region under Regions

                                                                                                                                                                                                                                                                        

2. In the Output point cloud region name prefix field, enter in a prefix for the new sampled point cloud region that will be created:

  

3. Click in the Point cloud region selection field and do either of the following:

 

a. To sample an entire point cloud region, select the region in the Project Explorer.

b. To sample a selection of scan points (as opposed to an entire region), select the Rectangle Select or Polygon Select tool in the status bar at the bottom of your TBC window and draw a rectangle or polygon around the scan points that you want to sample:

 

In this demonstration, I used the Polygon Select tool to select the scan points that I want to sample:

 

4. In the Sampling type drop-down list, select the appropriate sampling option: Spatial or Random:

 

a. If you select the Spatial sampling option, enter the sampling distance (space between each scan point) in the Spacing field. Spatial is the commonly used sampling type:

 

Note: A quick tip is that you can type in spacing value with a different unit, then TBC will convert it to the current project unit. 

b. If you select the Random sampling option, enter the total number of points to include in the sample in the Number of points to extract field (note that the unit is million points):

 

In this demonstration, I chose to use a Spatial sampling type with a Spacing of 0.050 meters.

   

5. Click the Store button:

 

The new sampled point cloud region is the only region displayed by default in the graphic view:

 

In addition, the newly sampled point cloud region displays in the Project Explorer:

 

My downsampled region is also added in the View Filter Manager under Point Cloud Regions, allowing us to turn the sampled region on and off. We can now use this downsampled region to create a surface. 

 

I hope this tip comes in handy next time you go to generate a surface in TBC!

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