Extract Cross-Sections from a Point Cloud

Use the Extract Cross-Sections from a Point Cloud command to create open or closed 3D cross-section line segments from a point cloud based on any of the following:

Two scan points - Select start and end scan points to create a line and extract a single cross-section along the line (for example, creating a contour line along a stockpile).
Reference lines - Select one or more linear objects (such as linestrings or CAD lines) to extract one or more cross-sections along the lines (for example, extracting underground mine profiles along predefined drilling/excavation reference lines).
An alignment - Select an alignment or other linear object (such as a linestring) and specify the intervals and offsets to use to extract one or more cross-sections perpendicular to the alignment or line (for example, extracting cross-sections along an alignment of a scanned roadway).

Prerequisites:

See the Subscription Plans page. For a license matrix by command, see the License page in the TBC Community. Also see View and manage licensed features.
This command assumes that the point cloud represents the surface of an object (for example ground or tunnel); therefore, it is highly recommended that you classify the point cloud and make unnecessary points invisible in advance. Unfiltered point cloud points can compute unexpected triangle meshes and can create unexpected cross-section lines.
To minimize processing time, it is highly recommended that prior to running this command you use the Sample Point Cloud Region command to create a new sampled region with the minimum amount of density required to create cross-sections successfully.
To extract point cloud points for cross-sections, the target point cloud points must be visible. Use the View Filter Manager as necessary.

To create cross-sections from a point cloud:

Select Extract Cross-Sections from a Point Cloud in Point Clouds > Extraction to display the Extract Cross-Sections from a Point Cloud command pane.
In the Extraction type drop-down list, select the appropriate option for extracting cross-section lines, and complete the fields as necessary:
- Two point cross-section - Select this option and then select start and end scan points to create a line to be used to create a single cross-section.
- Along reference lines - Select this option and then select one or more existing linear objects (such as linestrings) to be used to extract one or more cross-sections.
- Cross-sections on alignment - Select this option and then select an existing alignment or other linear object (such as a linestring) to be used to extract one or more cross-sections perpendicular to it. Optionally, do any of the following:
  - If you have selected an alignment, check either check box to specify to create a cross-section at each HAL and/or VAL point of intersection. (These check boxes are enabled only if an alignment is selected. They are not applicable for other linear objects.)
  - Change the default start and end station.
  - Enter a station interval at which you want to create cross-sections.
  - Enter a left offset (typically use a negative number) and right offset (typically use a positive number) from the selected line to be used to create the cross-section lines.
    Example using -5.000 left offset and 5.000 right offset:
    Example using -10.000 left offset and 10.000 right offset:
Select Settings as follows:
- Layer - Select the layer on which to display the cross-section lines. Or, select <<New Layer>> to create a new layer for the cross-section lines.
  You can use the layer properties to specify the style and color of the resulting cross-section lines. Following is an example where the lines were assigned to a new layer with the layer color set to green.
- Point cloud region - Optionally, select a single point cloud region to which the cross-section extraction will apply. Otherwise, select <None> to specify the extraction be applied to all visible regions.
- Search width - Specify the width from the selected line out to which the software will search for scan points to be used to extract the cross-section(s).
  Hint: Try experimenting. Depending on the density of the point cloud, a smaller search width (for example, 0.010) will reduce processing time and may still provide excellent results.
- Minimum segment length - Check this check box and specify the minimum distance between cross-section vertices. If vertices fall within this distance, they are removed, resulting in smoother lines.
- Include overhang - Check this check box to extract cross-sections from overhanging point clouds.
- Auto-close section lines - Check this check box to create closed linestrings for the extracted cross-sections when scan points cannot be located to complete the cross-section line. (Typically, you would select this option for tunnel point clouds which may not have scan points in the bottom of the tunnel.)
  Open cross-section lines:
  Closed cross-section lines:
Click the Apply button to create the cross-section line segments.
Cross-section linework displayed without a point cloud:
If you do not get satisfactory results, you can press Ctrl + Z to undo and try again.
To delete a cross-section, select its linework, right-click, and select Delete.
Note: If you extracted cross-sections from an alignment, the resulting cross-section linestrings will be named based on the stations where they were created.