Proper way to "downgrade" .las version?

[Jonathan Greenberg]

Hi there -- I've got a program that only works for LAS version 1.3 and earlier, and I have a file that is in 1.4.  What is the proper way to "downgrade" the point cloud to a version 1.3 (or earlier) version?

[Steeve Brissette]

I found this on google:

las2las -i input-las14.las -set_version 1.2 -o output-las12.las

Steeve Brissette 

Civil/Geomatics Technician 

TDB Consultants Inc.

Cell: 250-649-9846

On Sep 29, 2017, at 8:37 AM, Jonathan Greenberg <jgr...@gmail.com> wrote:

Hi there -- I've got a program that only works for LAS version 1.3 and earlier, and I have a file that is in 1.4.  What is the proper way to "downgrade" the point cloud to a version 1.3 (or earlier) version?

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[Kirk Waters - NOAA Federal]

Also best to check what you have first. If you have class numbers over 31 or other 1.4 specific info, you need to deal with that first.

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[Martin Isenburg]

Hello,

the most efficient way to "downgrade" a LAS 1.4 file to a LAS 1.3 file would be to simply rewrite the version number in the LAS heade in-place (i.e. without rewriting the file) as 1.3 using the corresponding '-set_version 1.3' option in lasinfo [1]. However, this will only result in a valid file when your LAS 1.4 file was storing LAS 1.3 content: the point type in your LAS 1.4 files (too bad you did not attach a lasinfo report [1] to your inquiry) needs to be between 0 and 5 and the so called "legacy point counters" need to be populated (i.e. not be zero).

If you have a LAS 1.4 file using the new point types then the simplest option would be to compress it with the "compatibility" mode of laszip (assuming your older software can read LAZ).This can be accomplished by calling

laszip -i las14.las -no_native -o las14_compatiblity.laz

The resulting 'las14_compatiblity.laz' file will then be a re-coded LAS 1.2 with all the LAS 1.4 parts hidden as extra bytes. The advantage here is that the additional LAS 1.4 content (more precise scan angles, higher return counts, scanner channel, overlap flag, ...) is not lost and can be recovered later.

To simply "downgrade" a LAS 1.4 file permanently to a LAS 1.3 file (or usually more appropriately to a LAS 1.2 file for point types 0 through 3) you can use the command line

las2las -i las14.las -set_version 1.2 -set_point_type 1 -o las12_downgraded.laz

But then any additional LAS 1.4 content (more precise scan angles, higher return counts, scanner channel, overlap flag, ...) is gone for good. However, I've come across quite a few LAS 1.4 files that were simply "upgraded" from a LAS 1.2 file because the tender specification said so. So maybe nothing will be lost after all. Again, too bad you did not attach a lasinfo report [1] to your inquiry as those always help to gain some more insight.

Regards,

Martin @rapidlasso

[1] http://rapidlasso.com/lasinfo