[Liblas-devel] LAZ / LAS extraction performance ... why does scene size make a difference?

[Howard Butler]

On Feb 2, 2011, at 1:23 PM, Michael Rosen wrote:

>  
>  
> I also ran some benchmarks on laz and yes, MG4.  I’d like to be able to collaborate with some of you on this effort.  I think MPG’s comments about the different target workflows are spot on.  For now, I do have an interesting observation about LAS and LAZ:  in both cases there seems to be a linear relationship between the cropped area the time it takes to do the extraction.  That would be expected if either
> (a)    there was some indexing support that told us where in the file the points were.  But I don’t believe there is any.

Definitely no index, at least not by default.  This is possible with using liblas::Index, but it is not so integrated into the rest of the utilities yet.  Speeding up windowed queries is definitely what that would be for, except it requires efficient random reads from the output, which .laz doesn't support right now.

> (b)   The process was dominated by output latency.  But I’m not creating output (specifying “-o –“ … which is what that’s for I assume)

You are creating output.  A las2las call without any output specified writes a 'output.las' file by default.