Table 7 The list of metrics derived from UAV-LiDAR point clouds

Height metric (22)

H01, H05, H10, H20, H25, H30, H40, H50, H60, H70, H75, H80, H90, H95, H99

Height percentile, all the normalized point clouds are sorted according to the elevation. HX is the Xth percentile of point cloud height

Hmax

Maximum height

Hmin

Minimum height

Hmean

Mean height

Hmedian

Median of height

H.cv

Coefficient of variation of height

H.ske

Skewness of heights

H.kur

Kurtosis of heights

Density metric (10)

D01, D02, D03, D04, D05, D06, D07, D08, D09, D10

Canopy return density, the point clouds are divided into ten slices of the same height from low to high. D01 to D10 corresponded to the point density from the lowest slice to the highest

Intensity metric (22)

I01, I05, I10, I20, I25, I30, I40, I50, I60, I70, I75, I80, I90, I95, I99

Intensity percentile, all the normalized point clouds are sorted according to the intensity. IX is the Xth percentile of point cloud intensity

Imax

Maximum intensity

Imin

Minimum intensity

Imean

Mean intensity

Imedian

Median of intensity

I.cv

Coefficient of variation of intensity

I.ske

Skewness of intensities

I.kur

Kurtosis of intensities

Vegetation Index metric (4)

LAI

Leaf Area Index, \(-\frac{\mathrm{cos}\left(\mathrm{ang}\right)\times \mathrm{ln}\left(\mathrm{G}.\mathrm{F}\right)}{\mathrm{k}}\), ang is the average scan angle, G.F is the gap fraction and k is the extinction coefficient

G.F

Gap Fraction, \(\frac{{\mathrm{n}}_{\mathrm{ground}}}{\mathrm{n}}\), ratio of ground points, less than 0.2 m in normalized cloud points, to all normalized cloud points

C.R.R

Canopy Relief Ratio, \(\frac{{\mathrm{H}}_{\mathrm{mean}}-{\mathrm{H}}_{\mathrm{min}}}{{\mathrm{H}}_{\mathrm{max}}-{\mathrm{H}}_{\mathrm{min}}}\)

C.C

Canopy Cover, \(\frac{{\mathrm{n}}_{\mathrm{vegfirst}}}{{\mathrm{n}}_{\mathrm{first}}}\), ratio of vegetation cloud points of first echo to all cloud points of first echo