Lidar drone systems are a particularly good choice for creating surveys over heavily vegetated areas. The laser pulses from a lidar unit not only hit the top of the vegetation but also the underlying ground or structures. Photogrammetric drone systems typically only capture the top of the canopy.


This article explains how to load point clouds into Virtual Surveyor. Virtual Surveyor automatically converts the point clouds to a terrain during the loading process.


Overview


Quick Guide

Virtual Surveyor converts the point cloud to an Elevation Terrain and/or an Image Terrain.  

  1. Select the point cloud. 
    1. Supported point cloud file formats are .las and .laz.
  2. Set a coordinate system or units because .las/.laz files often do not contain a coordinate system like GeoTIFF files do.
  3. Choose whether you want an Elevation Terrain, an Image Terrain, or both.
  4. Decide to favor high points (top of canopy) or low points (bare earth) or select the classes (if available) before starting the conversion.


Add a Point Cloud File

  1. Go to File and click New to create a New Project.
  2. Drag and drop the point cloud file(s); Virtual Surveyor will analyze the point cloud.
  3. When the analysis is complete, click Input Required to set the point cloud conversion options.
    Click Run to start the point cloud conversion
  4. First, define the Project Coordinate System. 
    1. You can enter the coordinate system name or EPSG code to easily find it in the list.
      Click classes to select the classes you want to use in your converted terrain

      or
    2. Tick the I don't know box and set the units to work in a Local Coordinate System.

  5. Choose your Point cloud settings. 
    1. You can generate multiple types of point cloud conversions simultaneously by selecting from the available options.
    2. Decide whether you want your point cloud conversion to include an Elevation Terrain, an Image Terrain, or both. 
      1. Image Terrain - only available when your point cloud contains RGB color information.
      2. Add Elevation terrain from low points  - creates a terrain with priority to bare-earth points.
      3. Add Elevation terrain from high points - a good option to model the top of a canopy.

      4. Add Elevation terrain from classes - only available when your point cloud contains classes.

  6. Click Run to start the conversion.
  7. When the conversion ends, click Insert to add the terrain(s) to the Viewport.

  8. Your data appears as a hillshade model or with the Image Terrain draped over the Elevation Terrain, depending on the Point cloud settings you chose to import.


Differences Between Elevation Terrains: Low Points and High Points

A lidar unit can create multiple points at the same horizontal location as a point cloud. The beam can either hit the vegetation or go through an interstice and measure a lower point. During the conversion of the point cloud to an Elevation Terrain, the user can force the points to favor either the high or low points.


Using high points is a good choice for modeling the tops of canopies. It can be used when you want to analyze tree heights or other vegetation features. 


Using low points gives a priority to bare-earth points. The resulting Elevation Terrain is not a perfect bare-earth surface and still contains spikes and structures like houses, but this process still reveals areas under the vegetation where the lidar beam was able to go through the canopy and hit the ground.


Add Multiple Point Cloud Files

When you add multiple point cloud files, Virtual Surveyor tests whether they overlap/touch or not. When they do overlap or touch, Virtual Surveyor merges the multiple point cloud files into one large elevation terrain.


Tips & Tricks

  • You can use the other terrain lenses to emphasize your terrain. Explore more About Terrain Lenses.
  • It also works for bathymetry data.
  • Point clouds from photogrammetry data? You can use them, but in this case it is better to use the orthomosaic (Image Terrain) and DSM (Elevation Terrain) from the photogrammetry process.


Watch the Video

Now that you have your point cloud imported, you can start with the real survey work. Learn how to generate contour lines from lidar data in the video below.