[GRASS-dev] Announcing libLAS

[Mateusz Loskot]

Hamish wrote:
> Mateusz:
>> Yes, it confirms what I've read in GRASS docs and Wiki pages,
>> that there is no direct support to ASPRS LAS format.
> ...
>> I'm willing to contribute a module for LAS read/write. However, I'm not
>> an experienced GRASS user nor developer, so I'll likely need to prepare
>> myself a little (read docs and code) before I can start. Means, I'm not
>> sure I can provide you with ready solution very soon.
> ...
>> The libLAS building follows well-known *nix patterns and there is 
>> autotools-based builder. Optionally, users are provided with cmake 
>> configuration as well as project files for Visual C++ 2005.
>> The library itself has no external dependencies.
> 
> Hi,
> 
> I don't claim to know anything about what libLAS does, so sorry if this
> doesn't make sense. But if it is purely vector format I/O would it be
> better to write it as a new format for GDAL's OGR and have grass access
> it with v.in.ogr? 

Hamish,

I agree that the LAS format is a vector format by data nature and 
structure. However, considering how LiDAR clouds are usually processed 
and analysed, they are closer to rasters and grids:
1. It's not uncommon to store millions of points in a single LAS file.
2. Mostly we are not interested in a single point feature but in 
groups/areas of hundreds or thousands
3. A feature-oriented seems not very usable

Technically, there is no problem with translating LAS file to OGR 
datasource and there is a prototype of appropriate tool [1] available,
but I'm not optimistic in its usability and *performance* in processing
of large sets of LiDAR data.

[1] http://liblas.org/svn/trunk/apps/las2ogr.cpp

> Or is the dataset size/model such that it is better to directly
> import/process it in GRASS using fast C modules as a front end to the
> lib?

Yes, this is my understanding. As a note of explanation, I'm not a very 
experienced user of LiDAR data, so I'm not able to explain the nature of 
processing and analysis of "huge clouds of points" datasets.
However, I understand that speed and performance is a critical factor.

Greetings
-- 
Mateusz Loskot
http://mateusz.loskot.net