All metrics were computed using functions within LASTools (https://rapidlasso.com/lastools/)
Processed by: Al Kirschbaum (al_kirschbaum@nps.gov)
Process date: September 2019

Collection dates: refer back to the county-specific LiDAR collection dates included in the original LiDAR metadata

Prior to creating forest structure rasters the following filters were applied to the original LiDAR data:
1) all points with scan angles greater than 20 degrees and less than -20 degrees were removed
2) all points with heights less than -2 feet and greater than 180 feet were removed

Horizontal resolution: 5 feet
Z (vegetation height): in feet

Point classes included in the creation of this project:
1: Unclassified
2: Ground
3: Low Vegetation
4: Medium Vegetation
5: High Vegetation

Description of canopy height raster
Using the raw (.las) lidar files for this area, I used lastools to create a smoothed canopy height raster. Each 5 ft x 5 ft pixel represents the height (in feet) of the tallest vegetation in this location. The workflow I followed is best outlined here: https://rapidlasso.com/2014/11/04/rasterizing-perfect-canopy-height-models-from-lidar/

The exact code I used in LAStools is included below...
set PATH=%PATH%;C:\LAStools\bin;
set BLOCK=K:\WI_County
set STEP=5
set SUBGRIDSTEP=1
set MIN_MAX=0 180
set CORES=6

lasindex -i -v %BLOCK%\Classified_LAZ\*.laz ^
    -cores %CORES%

lastile -i -v %BLOCK%\Classified_LAZ\*.laz ^
    -drop_scan_angle_above 20^
    -drop_scan_angle_below -20^
    -tile_size 2000 -buffer 200 -flag_as_withheld ^
    -odir %BLOCK%\laz_tiled -olaz ^
    -cores %CORES%

lasheight -i -v %BLOCK%\laz_tiled\*.laz ^
    -replace_z ^
    -classify_below -2 7 ^
    -classify_above 180 8 ^
    -odir %BLOCK%\tiles_normalized -olaz ^
    -cores %CORES%

lasthin -i -v %BLOCK%\tiles_normalized\*.laz ^
    -subcircle 2 ^
    -keep_class 1 2 3 4 5^
    -step %SUBGRIDSTEP% -highest ^
    -odir %BLOCK%\tiles_thinned -olaz ^
    -cores %CORES%

lasgrid -i -v %BLOCK%\tiles_thinned\*.laz ^
    -subcircle 2 ^
    -step %STEP% -highest ^
    -use_bb ^
    -odir %BLOCK%\tiles_values -odix "_vals" -oimg ^
    -cores %CORES%