How can I have the centroid of each chunk of a catalog?

Question

I use lidR package. I have a catalog and I want to save as a shapefile the centroid of each chunk make with opt_chunk_size of a catalog ?

Answer 1

There may be a better way to do this, but a combination of lidR functions and the sf package should work. Try the following:

ctg <- readLAScatalog("~/Documents/data/lidar/example_catalog/")
opt_chunk_size(ctg) <- 1000
plot(ctg, chunk=TRUE)
chunks <- catalog_makechunks(ctg)
library(sf)
centroids <- lapply(chunks, function(chunk) {
  return(st_point(x=c(chunk@center$x, chunk@center$y)))
})
centroids_shape <- st_as_sfc(centroids)
plot(centroids_shape)
st_write(centroids_shape, "/tmp/test.shp")

Plot of catalog:

Plot of un-chunked centroids:

Plot of chunked catalog:

Plot of chunked centroids:

Overlay of chunks, and their centroids:

** UPDATE ** - As mentioned by @JRR, you will need version 3.0.0 of the lidR package to use catalog_makechunks() which I believe is currently in development. In older versions you must use the internal function lidR:::catalog_makeclusters(). To get version 3.0.0 of lidR you can run:

library(devtools)
install_github("Jean-Romain/lidR", ref = "devel")