lidR: center chunks when retiling

Question

I want to retile big TLS files into quite small chunks of maximum 20 m x 20 m size. I have to normalize the point cloud, thus I need to classify the points and create a DTM for each tile. For this process, especially smaller tiles seem to cause me trouble (I guess it's hard to fit  a plane in only few points). But I noticed when splitting up the data into chunks, there are quite many chunks with only little information.
ctg <- readTLSLAScatalog(path_points)
opt_chunk_buffer(ctg) <- 0
opt_chunk_size(ctg) <- 20
plot(ctg, chunk=TRUE)

Can I somehow reposition the tiles so the bottom left corner of the data is also the bottom left corner of the first chunk? Or (even better) a possibility to center the tiles and the chunks so all chunks on the borders have similar sizes? I saw there is an option opt_chunk_alignment(), but I don't understand how it works exactly. Also, I guess I could play around with the chunk size because it might help, but I want to automize the process for several LAS files.

JRR · Accepted Answer

I want to retile big TLS files into quite small chunks of maximum 20 m x 20 m size

I don't know what kind of problem you are trying to solve be it sounds like a bad idea. Moreover you can do it on-the-fly without physically splitting your data.

Can I somehow reposition the tiles so the bottom left corner of the data is also the bottom left corner of the first chunk? [...] I saw there is an option opt_chunk_alignment(), but I don't understand how it works exactly.

It does exactly what you want to do.
opt_chunk_alignment(ctg) <- c(min(ctg$Min.X), min(ctg$Min.Y))

Or (even better) a possibility to center the tiles and the chunks so all chunks on the borders have similar sizes?

There is no such option and I'm not sure to understand what you are expecting actually.

lidR: center chunks when retiling

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