#Get the list of LAS files to work with
files <- list.files(path = "/...2015TestGroup", full.names = TRUE,  recursive=FALSE)

#Set up the catalog properties
ctg <- catalog(files)
opt_chunk_size(ctg) <- 500
opt_chunk_buffer(ctg) <- 20
opt_output_files(ctg) <- ".../Outputs/2015nonground/{XLEFT}_{YBOTTOM}_2015"

#Select only those points not classified as "ground"
aboveground <- lasfilter(ctg, Classification != 2L)

#Get the list of 2015 "non-ground" points
files <- list.files(path = ".../2015nonground", full.names = TRUE,  recursive=FALSE)
#Set up the catalog properties
ctg <- catalog(files)
opt_output_files(ctg) <- ".../2016thinned/{XLEFT}_{YBOTTOM}_2015"

#Thin the points so they are consistent with the 2007 data
thinned <- lasfilterdecimate(ctg, homogenize(1, 1))