Rescaling LAS file with lidR package in R? [duplicate]

Question

I am trying to process a large .las file received, which appears to have been scaled in non-standard ways for some reason (likely data transfer portability). The scales between x, y, z are different in and in the range of 10^-5 instead of 0.01 or so. The odd scales in non-standard values prevents me from processing or writing the LAS files with writeLAS or other commands, with an error of:

Error: Invalid header: X scale factors should be factor ten of 0.1 or 0.5 or 0.25 not 1.06228168611949e-05

Is there a good way to actually rescale the point cloud with the lidR package?

I know that the scale factors can be accessed through the header information, as per the code and output from sample LAS file below.

I also seek additional discussion on what it means to rescale the point cloud, and what should be used for physical interpretation and writing to DEMs rather than storage.

Sample reading in and displaying header info in R:

    LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
    las <- readLAS(LASfile)
    las@header
    # las@header@PHB

Output includes:

Scale factor X Y Z:       0.01 0.01 0.01 

Currently using lidR version 2.02 and rlas version 1.3.1.

Answer 1

lidR should not throw an error for that, at read time. It is invalid but not corrupted so it is readable. However writeLAS do throw an error. You have two solutions. The first one should be preferred in my opinion.

Fix your original files with las2las from lastools. las2las should be preferred for every tasks that imply las file processing. Use:

 las2las -i *.las -rescale 0.01 0.01 0.01

The other option, if you have already read your file in R. Fix manually the header.

las <- readLAS("file.las")
las@header@PHB[["X scale factor"]] <- 0.01
las@header@PHB[["Y scale factor"]] <- 0.01
las@header@PHB[["Z scale factor"]] <- 0.01
writeLAS(las, "file2.las")

Edit: lidR 2.1.3 will have two new functions lasrescale() and lasreoffset(). See on github.