What is LiDAR?

Light detection and ranging (LiDAR) is an active remote sensing method that creates 3D point cloud datasets from emitted pulses of light. The LiDAR unit emits pulses of light that reflect from objects and return to the unit’s sensor. The difference in time between each light pulse emitted and returned creates a location in space. Each location is in x,y,z coordinates, called a “point” and when combined together, called a “point cloud.” LiDAR units produce thousands of measurements (or points) per second resulting in rich datasets containing millions of 3D points. We use both terrestrial laser scanning (TLS) and airborne laser scanning (ALS), tailoring each for specific monitoring needs. TLS units come in many forms (i.e. hand-held mobile scanners, tablet scanners, etc.) and we focus here on tripod mounted stationary TLS units. As such, TLS in our case is used to sample the fine-scale (sub-cm resolution) 3D structure of vegetation in a typical forestry plot (~0.1 ha) that can be linked to fuels measurements, forestry inventory and ecological data. ALS is used to sample coarse-scale (sub-m resolution) 3D structure of vegetation and topography across stands to landscapes (1,000’s of ha) that can be used to estimate tree canopy metrics (tree locations, heights, canopy profiles) and even detect cultural resources across large areas. ALS can be linked to surface vegetation and fuels captured by TLS data. 
     

TLS and ALS landscape monitoring techniques can improve reliability and repeatability of measurements by drastically removing bias and error, and can be coupled with traditional field measurements to compliment or amplify a monitoring program. TLS scans can be uploaded, archived, and analyzed repeatedly, even as processing scripts and instruments evolve, improving replicability and standardization of monitoring methods.