Overview

Subset LiDAR Data clips a LAS/LAZ point cloud to a user-defined boundary. The tool first shows the data extent in the drawing (displayed as a red outline) so you can confirm coverage, then you select (or draw) a closed polygon to define the area of interest. SPCAD creates a new output LAS file containing only the points inside the boundary. 

Access 

LiDAR Tools → Subset LiDAR Data 
Command: LASCLIP_SP 

What does the Suubset Lidar Data do? 

• Lets you choose an input LAS/LAZ file. 
• Draws the LiDAR file extent in the drawing (red boundary) for visual reference. 
• Prompts you to provide a clip boundary: 
  • Select an existing closed polyline, or 
  • Use Draw to sketch a closed polygon on-screen. 
• Clip the point cloud to the boundary. 
• Prompts you to choose an output LAS file location/name and saves the subset. 

Workflow 

1. Run LASCLIP_SP. 
2. Select the input LAS/LAZ file. 
3. SPCAD displays the file’s extent in the drawing (red). 
4. When prompted, define the clip boundary: 
   • Select an existing closed polyline, or 
   • Type Draw and draw a closed polygon. 
5. Choose the output LAS file path and name. 
6. SPCAD creates the subset LAS file. 

Usability notes 

• Ideal for extracting project/site-area points from a large LiDAR dataset before: 
  • creating DEM/DSM, 
  • building TIN surfaces, 
  • running tree/building extraction, 
  • performing thinning or slicing. 
• The red extent preview helps you quickly verify that the LAS coverage matches your drawing area. 

Tips 

• Use a closed boundary: The clip polygon must be a closed polyline. If clipping fails, verify the polyline is closed and not self-intersecting. 
• Keep the boundary within the red extent: If your polygon is outside the LAS coverage, the output may be empty or incomplete. 
• Smaller boundary = faster output: Clipping a huge region can still be large; clip to the smallest practical area for better performance. 
• Save with a clear name: Use naming like SiteA_Subset.las or Corridor_Clip.las to keep multiple subsets organized. 
• Work in the correct coordinate system: The boundary should be in the same coordinate space as the LAS data. If the extent preview appears far away or scaled incorrectly, check your drawing units/coordinate system setup. 

Output 

• A new LAS file containing only the points inside the selected/drawn polygon. 
• The extent outline is only a visual reference and does not modify the original LAS file.