Changing point values in place

[Suresh Babu Jakka]

Hello all,

I am new to LAZ api and learning it now. It is really straight forward and easy to pick it up. 

I am trying to classify bunch of points in LAZ file in place. I run an algorithm on bunch points and classify them if needed in place. Is it possible using LAZ api? I could not find anything related to this in examples. Do I need to un-compress  LAZ file to LAS, classify the points and then compress it?

Thank you and appreciate your help,

Suresh

[Andrew Bell]

Yes.  You can't change values of point attributes directly in a LAZ file.

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Andrew Bell
andrew....@gmail.com

[Suresh Babu Jakka]

Thank you for the quick reply.

[Suresh Babu Jakka]

Hello,

Is it possible to read a block of data from LAZ file, modify the point data and write back that block of data in place to LAZ file?

I am guessing we cannot do it, but wanted to confirm it.

Thank you for your help,

Suresh

On Thursday, September 7, 2017 at 11:41:43 AM UTC-5, Andrew Bell wrote:

[Martin Isenburg]

Hello,

I guess you mean per "compressed unit" and that is called a "chunk" in LASzip lingo. No. That is not possible as the size of the compressed chunk may not be the same as before. Compression and therefore compressed chunk size varies with point content. When you change the content of one or more points in the chunk thrn you are likely to change the size of the entire compressed chunk.

In LAStools I use the concept of LASlayers [1] to log small changes in compressed files. But that is not part of LASzip.

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

Regards,

Martin @rapidlasso

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