TITLE: Pretty pictures from Terrestrial LiDAR
DATE: 2021-04-20
AUTHOR: John L. Godlee
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I've been trying to extract tree canopy complexity statistics from 
my terrestrial LiDAR data. As part of this I have been creating 
Canopy Height Models (CHMs) for each of my savanna plots. This 
involves "pit-filling" to remove low points where the LiDAR didn't 
penetrate all the way to the top of the canopy. Without 
pit-filling, the canopy surface appears pock-marked and jaggedy, 
while I want to approximate the top of the canopy as an even 
surface. So basically, in order to pick the best pit-filling and 
canopy height model algorithms, I have been making lots of maps and 
3D surfaces of the tree canopy surface. I'm not going to get into 
the maths behind what I did, I just wanted to share some pretty 
pictures that came out of this process. Note, all these images are 
from the same plot, in Bicuar National Park, southwest Angola.

  ![99th percentile of height from raw point cloud data, following 
noise removal and 
voxelisation](https://johngodlee.xyz/img_full/lidar_art/raw.png)

  ![Predicted values from a generalised additive model of canopy 
height](https://johngodlee.xyz/img_full/lidar_art/gam.png)

  ![Canopy height after 
pit-filling](https://johngodlee.xyz/img_full/lidar_art/pit.png)

  ![Topographic roughness 
index](https://johngodlee.xyz/img_full/lidar_art/topo.png)

  ![Topographic roughness index, using a more coarse 1 m^2 
resolution](https://johngodlee.xyz/img_full/lidar_art/topo_coarse.pn
g)