Converting LiDAR files from LAZ to LAS format

Question

I'm trying to convert LiDAR files from the LAZ format (the compressed version) into LAS (the uncompressed version) using LASzip software.

However, I am not really sure how it works. I created a new output folder as I entered in the app interface, but it is totally empty.

I also had tried the following code in the command prompt window:

 D:\LiDAR\Laszip\laszip.exe *.laz 

and got a message saying 'no input specified'.

In my folder, there are about 100-ish.laz files as well as one imu.laz. Any suggestions?

Answer 1

For running LASzip from the command prompt window it is also necessary to specify the path of the input file.

For example, suppose the laszip.exe file is installed under the drive D: (D:\LASzip\laszip.exe) and that the .laz files are stored in D:\lidar.

Then, type:

D:\LASzip\laszip D:\lidar\*.laz

It will decompress all LAZ files in the current folder overwriting any existing file. The output files will have same name as the input files (but with extension .las).

Some remarks:

• it is not necessary to type the file extension '.exe' in the command-line.
• one can also use the identifier -i for input parameter, but it is optional: D:\LASzip\laszip -i D:\lidar\*.laz.
• the identifier -odir can be used to specify a different output folder: D:\LASzip\laszip -i D:\lidar\*.laz -odir D:\lidar\output. It will save all .laz files with the same file names (except for .las extension) in the specified output folder. See Saving LAZ files to different location from input (LAS) files?.
• use the identifier -odix to append to output file names: D:\LASzip\laszip -i D:\lidar\*.laz -odir D:\lidar\output -odix _decompressed. It means if the input file name is point_cloud_27.laz, the output file name will be point_cloud_27_decompressed.las.

See more examples here.

Another option (in relation to first example) is to proceed as suggested by Barbarossa, i.e., open the cmd from the input file folder and write the command as in your first attempt.

REM move to folder where the input file is, then run laszip.
cd  D:\lidar
D:\LASzip\laszip *.laz

If you want to call laszip directly from any folder without specifying the program path, then, berniejconnors's answer gives a good hint to add it in the environment variables (see here).

laszip D:\lidar\*.laz 

---

All examples here work the other way around, i.e., converting from .las files to .laz.

Answer 2

To run laszip in a command prompt in Windows you need to use the "-i" paremeter to specify your input files:

laszip -i lidar.laz

or

laszip -i *.laz

To run the above commands Laszip must be in your PATH environment variable:

set path=%path%;<path_to_your_laszip_exe>
set path=%path%;C:\LAStools\bin

And the laz files must be in your current directory.

If your input file(s) has the LAZ extension laszip will uncompress the files. If your input file(s) has the LAS extension laszip will compress the files.

If you have the full install of LAStools you should have a "laszip_README.txt" file with numerous command line examples.

There is a LAStools Google Group where you will get great support from expert users and Martin Isenburg, the creator of LAStools and LASzip.

Answer 3

It seems you are running on windows. Simply double-click the laszip.exe program and operate it via the GUI. You can browse to the folder you want to decompress via the 'browse...' rollout on the left side of the menu. Why are you needing to decompress LAZ to LAS? Is there a software you want to use that does not support LAZ natively? Which one? Check this and that YouTube playlist of videos for many tutorials on how to use LAStools ...