Vertical Complexity Index

[Ben Pearse]

Hi there, 

I'm trying to understand the VCI a bit more. I have read the paper "Comparison of forest structure metrics derived from UAV lidar and ALS data" by Bruggisser et al 2019 and understand that VCI describes "the evenness and vertical distribution of points across the canopy layers". 

My understanding is that using lascanopy you can set the bin size e.g. -vci 1 2 4, would give me bin sizes of 1, 2, and 4 meters, but I don't understand how VCI is being calculated for each dataset or polygon. 

For example, I have two datasets, one with conifer trees (~ 6 m tall) and another with lower lying shrubs (~ 1.5 m tall), each consisting of ten polygons. For each polygon in my conifer dataset the VCI is roughly 0.8 and in each polygon of my shrub dataset the VCI is roughly 0.75. I would expect those values to be more different given the differences in heights. Is the VCI measuring the evenness and vertical distribution of points based on the maximum  height in each polygon?

Thanks for your help, hopefully that makes sense, 

Ben