Why are opt_chunk_buffer(ctg) <- 0 opt_chunk_size(ctg) <- 10000 being added? And why the value 0 and 10000?

When processing a LAScatalog you define a chunk size to process sequentially small chunks that fit in memory. Your chunks can be smaller than your tiles, the size of your tiles or bigger than you tiles. If you put a number bigger than the size of your collection it mean that it processes everything at once into a single massive chunk. Here the value 10000 is totally arbitrary. You can put 100000. Just put a number big enough such a only one chunk is generated.

The buffer is 0 because you don't need to load redundant data between the chunks. Anyway there is only one chunk. If what I'm saying is not clear, I suggest reading this chapter of the book.

And this singlefile_ctg <- catalog_retile(ctg) will write the merged LAS file into the same folder as given in ctg = readLAScatalog("folder/")? Because my output path is different from the input folder.

No. It will write into folder/singlefilename.las. Again read the book chapter linked.

On a side note when I run readLAScatalog(), I get the following warning, I don't know if this is going to be an issue while merging the files.

It depends if they are duplicated points. If two files overlap and each one contains a subset of points that can be found in both files (typically files in which a buffer has been added) yes it is a problem. If the bounding boxes overlap but the actual point cloud is continuous without duplicated region it is not a problem.

Why are opt_chunk_buffer(ctg) <- 0 opt_chunk_size(ctg) <- 10000 being added? And why the value 0 and 10000?

When processing a LAScatalog you define a chunk size to process sequentially small chunks that fit in memory. Your chunks can be smaller than your tiles, the size of your tiles or bigger than you tiles. If you put a number bigger than the size of your collection it mean that it processes everything at once into a single massive chunk. Here the value 10000 is totally arbitrary. You can put 100000. Just put a number big enough such as only one chunk is generated.

The buffer is 0 because you don't need to load redundant data between the chunks. Anyway there is only one chunk. If what I'm saying is not clear, I suggest reading this chapter of the book.

And this singlefile_ctg <- catalog_retile(ctg) will write the merged LAS file into the same folder as given in ctg = readLAScatalog("folder/")? Because my output path is different from the input folder.

No. It will write into folder/singlefilename.las. Again read the book chapter linked.

On a side note when I run readLAScatalog(), I get the following warning, I don't know if this is going to be an issue while merging the files.

It depends if there are duplicated points. If two files overlap and each one contains a subset of points that can be found in both files (typically files in which a buffer has been added) yes it is a problem. If the bounding boxes overlap but the actual point cloud is continuous without duplicated region it is not a problem.

Why are opt_chunk_buffer(ctg) <- 0 opt_chunk_size(ctg) <- 10000 being added? And why the value 0 and 10000?

When processing a LAScatalog you define a chunk size to process sequentially small chunks that fit in memory. Your chunks can be smaller than your tiles, the size of your tiles or bigger than you tiles. If you put a number bigger than the size of your collection it mean that it processes everything at once into a single massive chunk. Here the value 10000 is totally arbitrary. You can put 100000. Just put a number big enough such a only one chunk is generated.

The buffer is 0 because you don't need to load redundant data between the chunks. Anyway there is only one chunk. If what I'm saying is not clear you suggest reading this chapter of the book.

And this singlefile_ctg <- catalog_retile(ctg) will write the merged LAS file into the same folder as given in ctg = readLAScatalog("folder/")? Because my output path is different from the input folder.

No it will write into folder/singlefilename.las. Again read the book chapter linked.

On a side note when I run readLAScatalog(), I get the following warning, I don't know if this is going to be an issue while merging the files.

It depends if they are duplicated points. If two files overlap and each one contains a subset of points that can be found in both files (typically files in which a buffer has been added) yes it is a problem. If the bounding boxes overlap but the actual point cloud is continuous without duplicated region it is not a problem.

Why are opt_chunk_buffer(ctg) <- 0 opt_chunk_size(ctg) <- 10000 being added? And why the value 0 and 10000?

When processing a LAScatalog you define a chunk size to process sequentially small chunks that fit in memory. Your chunks can be smaller than your tiles, the size of your tiles or bigger than you tiles. If you put a number bigger than the size of your collection it mean that it processes everything at once into a single massive chunk. Here the value 10000 is totally arbitrary. You can put 100000. Just put a number big enough such a only one chunk is generated.

The buffer is 0 because you don't need to load redundant data between the chunks. Anyway there is only one chunk. If what I'm saying is not clear, I suggest reading this chapter of the book.

And this singlefile_ctg <- catalog_retile(ctg) will write the merged LAS file into the same folder as given in ctg = readLAScatalog("folder/")? Because my output path is different from the input folder.

No. It will write into folder/singlefilename.las. Again read the book chapter linked.

On a side note when I run readLAScatalog(), I get the following warning, I don't know if this is going to be an issue while merging the files.

It depends if they are duplicated points. If two files overlap and each one contains a subset of points that can be found in both files (typically files in which a buffer has been added) yes it is a problem. If the bounding boxes overlap but the actual point cloud is continuous without duplicated region it is not a problem.