R LidR Export – How to Export a lidR LAScatalog to a Shapefile

lidrr

I would like to export a lascatalog to a shapefile. It could be done in the past with rgdal but this is being retired.

The error is below.

library(lidR)
library(sf)
ctg <- readLAScatalog(system.file("extdata", "MixedConifer.laz", package="lidR"))
st_write(as(ctg, "sf"), "ctgIndex.shp")
#> Error in as(ctg, "sf") : 
#>  no method or default for coercing “LAScatalog” to “sf”

Best Answer

Use sf::st_as_sf instead of as(ctg, "sf") before to write with sf::st_write

Note: sf::st_as_sf simply returns ctg@data which IS an sf object.

Related Solutions

lidR – Resolving Issues with Classifying by Shapefile Using merge_spatial in lidR

You were almost there but you made some R errors. Below a full reproducible example

shp_merge_spatial = function(las, shp) UseMethod("shp_merge_spatial", las)

shp_merge_spatial.LAScluster = function(las, shp) {
  # The function is automatically fed with LAScluster objects
  # Here the input 'las' will a LAScluster
  
  las <- readLAS(las)                          # Read the LAScluster
  if (is.empty(las)) return(NULL)              # Exit early (see documentation)
  
  las <- merge_spatial(las, shp, attribute = "in_poly")      # merge_spatial
  las$Classification[las$in_poly] <- LASBUILDING           # classify
  return(las)                             # Return the point cloud
}

shp_merge_spatial.LAScatalog = function(las, shp){
  opt_chunk_buffer(las) <- 0
  catalog_sapply(las, shp_merge_spatial, shp = shp)
}

library(lidR)

LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
ctg = readLAScatalog(LASfile, chunk_size = 150)

shp   <- system.file("extdata", "lake_polygons_UTM17.shp", package = "lidR")
lakes <- sf::st_read(shp)

opt_output_files(ctg) <-"{tempdir()}/{ID}_bldg_cls"
output <- shp_merge_spatial(ctg, lakes)

plot(output)
las = readLAS(output)
plot(las, color = "Classification")

This is a bit complex because merge_spatial does not have LAScatalog variant. But in lidR 3.2.0 that will be released probably next week there is classify_poi()

library(lidR)

LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
ctg = readLAScatalog(LASfile, chunk_size = 150)

shp   <- system.file("extdata", "lake_polygons_UTM17.shp", package = "lidR")
lakes <- sf::st_read(shp)

opt_chunk_size(ctg) <- 150
opt_output_files(ctg) <-"{tempdir()}/{ID}_bldg_cls"

output = classify_poi(ctg, LASBUILDING, roi = lakes)

plot(output)
las = readLAS(output)
plot(las, color = "Classification")

Best Answer

Related Solutions

lidR – Resolving Issues with Classifying by Shapefile Using merge_spatial in lidR

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