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.
- Select the point cloud. Supported point cloud file formats are .las and .laz.
- Set a coordinate system or units because .las/.laz files do not carry a coordinate system like GeoTIFF files do.
- Choose whether you want an elevation terrain (DSM), an image terrain (orthophoto), or both.
- Decide to favor high points (top of canopy) or low points (bare-earth), or select the available classes (if available) before starting the conversion.
Add a point cloud file
- Go to File and click New to create a new (empty) project.
- Drag & drop the point cloud file(s). Virtual Surveyor analyzes the point cloud first.
- When the analysis is complete, click Input Required to set the point cloud conversion options.
- First, define the coordinate system. You can enter the coordinate system name or EPSG code to easily find it in the list. Click the I don't know box to add a check and set the units if you prefer to work in a local coordinate system.
- Choose the create settings. Decide whether you want to convert the point cloud to an elevation terrain and/or an image terrain. The image terrain option is only shown when your point cloud contains color information.
- Finally, set the conversion option. Favor high points is a good option to model the top of a canopy. Favor low points gives priority to bare-earth points. You can also decide which classes to import. The Select classes to include option only shows when your point cloud contains classes.
- Click Run to start the conversion.
- When the conversion ends, click Insert to add the terrain(s) to the viewport.
- Your data will appear as a hillshade model or with the orthophoto draped over the elevation terrain.
Favor high points or favor low points
A lidar unit can create multiple points at the same horizontal location in a point cloud. Indeed, the beam can either hit the vegetation or go through an interstice and measure a lower point. The user can force the points to favor during the conversion of the point cloud to an elevation terrain.
Favor high points is good for modelling the tops of canopies. It can be used when you want to analyze tree heights or other vegetation features.
Favor low points gives 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 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 will test if they overlap or touch. When so, the multiple point cloud files will be merged into one large elevation terrain.
Tips & Tricks
- You can use the other terrain lenses to emphasize your terrain. Explore all the terrain lenses here.
- 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 orthophoto and DSM 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.