LiDAR drones are gaining popularity in the land surveying market. These systems are a particularly good choice for creating surveys over heavily vegetated areas.
The laser pulses from a LiDAR unit hit not only the topcover vegetation of an area, but also the underlying ground or structures. While photogrammetric drone systems typically capture only the top of vegetation.
This article explains how these point clouds can be loaded and converted in Virtual Surveyor.
- Select the point cloud. Supported point cloud file formats are .las and .laz.
- Set a coordinate system or units because .las/.laz don’t 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 you can 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 first analyzes the point cloud.
- When the point cloud analysis is completed, click on Input Required button to set the point cloud conversion options.
- Define the coordinates system. You can enter the coordinates system name or EPSG code to easily find it in the list. Check "I don't know" and select the units if you prefer to work in a local coordinate system.
- Choose the point cloud settings.
- Decide whether you want to convert the point cloud to an elevation terrain, an image terrain or both.
- Choose the conversion option. Favor high points is good to model top of canopy. Favor low point gives priority to bare-earth points. You can also decide which classes to import.
- The options available in the point cloud settings window depend on the features of the point cloud file.It is only possible to generate an image terrain when the point cloud contains color information.
It is only possible to select classes to include when the point cloud has previously been classified.
- Click Run to start the conversion.
- Only the points selected according to the conversion option will be used.
- Holes will be interpolated.
- When the conversion ends, Insert the terrain in the view port.
- The image terrain is draped over the elevation terrain.
- The hill shade lens is automatically enabled if no image terrain has been generated from the point cloud
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 thanks to multiple drone positions and angles. The user can force the points to favor during the conversion of the point cloud to an elevation terrain.
Favor high points is good to model top of canopy. 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 some spikes. But this process reveals areas under the vegetation where the LiDAR beam was able to go through canopy cracks 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 use the Virtual Surveyor toolbox to generate a lightweight CAD model. In this video, contour lines are generated at bare earth [with Zenmuse L1].