[gdal-dev] Gdal-Grid lidar.

[Nicolas Cadieux]

Hi,
I have been using gdal_grid to interpolate LiDAR data for some time now.  This would be a typical command:

gdal_grid -l P0344_sol2004_XYZI_MTM8_CGVD28_150529 -txe 348733.0 401135.0 -tye 5568587.0 5773796.0 -a nearest:radius1=3.0:radius2=3.0:angle=0.0:nodata=0.0 -outsize 52402.0 205209.0 -of GTiff H:/Nicolas/pytemp/OutPut\P0344_sol2004_XYZI_MTM8_CGVD28_150529.vrt H:/Nicolas/pytemp/OutPut\P0344_sol2004_XYZI_MTM8_CGVD28_150529.tif --config GDAL_NUM_THREADS ALL_CPUS

As you can see, this is a huge raster and the csv. file (Pointed with a .vrt) contains over a billion points.  I am trying to do this in one shot to avoid boundary effects.  (I know I can split this .csv file into smaller bits and make this more efficient).   The computer I am using has 12 cores, 64BG of memory (smaller than the csv file) and a 1TB pcie solid state drive.  It should manage the task but it has been running for 5 days with less than 10% done).  I have access to a super computer with gdal if all else fails.    

This is my question.  The "--config GDAL_NUM_THREADS ALL_CPUS" or "--config GDAL_NUM_THREADS 12" does not seem to work with the nearest neighbor algorithm. (It seem to work with the -a count command)  If I use this on a smaller data set, I see no difference in speed or cpu usage between using the "ALL_CPUS" or not using this switch.  Is this a bug or simply a limitation of the nearest neighbor algorithm?  I don't want to move this to a super computer if it will not multi-thread properly.  

Thanks,
Nicolas Cadieux

(Gdal1.11.2 downloaded with OSGEO4W 64bit install with QGIS 2.8 on windows 7_64)  I use GDAL from the command line not from QGIS.


Nicolas Cadieux M.Sc.
Les Entreprises Archéotec inc. 
8548, rue Saint-Denis Montréal H2P 2H2
Téléphone: 514.381.5112  Fax: 514.381.4995
www.archeotec.ca