Create one single DTM raster file from multiple LAS files

Question

This question can be considered an extension of Create a DTM using the TIN algorithm

I am providing multiple LAS files as a catalog list to the rasterize_terrain which breaks the LAS into smaller chunks and returns DTM .tif rasters for each chunk.

The I have to use the terra package to merge these smaller DTM rasters into one big raster. Now is there a way to directly get a single DTM raster using just the lidR package? Or is there a better way to do this or is my current code the correct approach?

I did try merging (catalog_retile() function) all input LAS files into a single LAS to get a single DTM raster, however rasterize_terrain failed with an interpolation error. So, I guess it is best to use multiple LAS files.

Current code:

library(lidR)
library(terra)
 
# Create a LAS catalog
LAS_List = readLAScatalog("path", recursive = TRUE)

# Create an output destination to store the DTM raster files
opt_output_files(LAS_list) <-  paste0("folder/{*}_dtm")

# Create a DTM using the TIN method
dtm_tin = rasterize_terrain(LAS_List, res = 1, algorithm = tin())

# Create a list of rasters and store their path
FL_DTMs_List = list.files(getwd(), "tif$", full.names=TRUE) # the $ exludes aux-files

# Create a SpatRasterCollection using the terra package
DTM_ic = sprc(lapply(FL_DTMs_List, rast))

# Merge these DTMs into a single raster
terra::merge(DTM_ic, filename = "path/DTM/DTM.tif") 

Answer 1

It is not possible in lidR and it is not useful. You have multiple raster files and a virtual raster mosaic file to "glue" them. Any decent gis software including R is able to handle virtual raster mosaic as a single raster. If you really want a single raster file then you can use terra::writeRaster.

terra::writeRaster(dtm_tin, "path/DTM/DTM.tif")