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I am using lidR to create a DEM of a very large area (over 1 million hectares). I have already processed a portion of this area.

I would like to be able to read the entire LAScatalog so that the tiles I still need to process can access bordering tiles and use them as buffers, but don't know how to avoid processing the rest of the catalog.

I have been looking at the partial processing option as well as the catalog_intersect() function. I can make a raster of the area that I have already processed and get the extent and use catalog_intersect() to eliminate the tiles I have already processed, but that would also remove the tiles that would be needed as buffers.

Is there a way to use the ctg$processed option to select only the area not covered by a particular extent or spatial object for processing? Or is there a way to access the numbers assigned to each chunk of the catalog so that I can export the spatial object, intersect it with the processed area, and then use the ctg$processed option to select the unprocessed area?

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You can either use catalog_select(..., method = "flag_unprocessed") to interactively click on tiles you don't want to process (those that will be used as buffer only) or you can convert your LAScatalog into a pure SpatialPolygonsDataFrame to apply geometry operations. Below an example removing 10 km to the bounding box of the collection.

library(lidR)
ctg <- readLAScatalog("folder/")

bbox <- extent(ctg) - 10000
bbox <- as(bbox, 'SpatialPolygons')  
spctg <- as.spatial(ctg)
ctg$processed <- rgeos::gIntersects(bbox, spctg, byid = TRUE)
plot(ctg)

Created on 2020-04-15 by the reprex package (v0.3.0)

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  • Fantastic, thank you! This worked perfectly. – KLH Apr 16 at 6:20

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