LEGO Lidar Part 4: Measuring Trees

Forestry science takes interest in the height and leaf content of trees. The height of a tree and the dimensions of the leaf canopy can give insight on the health, age, and biomass content of the tree. Such measurements can be easily made with a scanning lidar. As a demonstration, the tree in the photo above was scanned with the hardware configuration of my post “LEGO Lidar”, but with the lidar turned at a right angle to scan a vertical slice. I placed the lidar in the back of my car, with the hatchback up as in the photo below.

The result of the scan is shown below in a polar plot. With the lidar pointed in azimuth to hit the trunk of the tree, the trunk is clearly seen in the scan. Several conclusions can be made from this data: (1) the height of the tree is 19.2-meters, (2) the leafy canopy extends from a height of 3-meters to 19.2-meters, and (3) the diameter of the canopy at the widest point (called “crown spread” in forestry lingo) is 15-meters. Scanning up and down the tree multiple times, as was done in the data below, allows for occasional lidar pulses to view through leaves and branches from minor variations of the scan angle.