I don't find it to be particularly slow .... I guess it depends on how much processing you have to do. My uses are fairly limited so it's not a problem.
Not quite on topic, but close, and something I'm trying to figure out -- the LibLAS decoded file can provide all of the point data - not just x,y,z. This includes identification of 1st and 2nd arrivals which helps a lot in discerning vegetal cover from the ground surface. However, if you are going to filter on arrival time to get a ground surface data set you have to eliminate the 1st arrivals - but only if there's a second. If a second is absent (no vegetation at that location) then the 1st becomes the 'last' too. This makes interpretation more complicated and not just a matter of separating the 1s and 2s. I ended up writing a short script in octave to split the data into two pools - first arrivals and true last arrivals using the simple notion that a 1 is only a first if it is followed by a 2. If not, it's a last. Has anyone else wrestled with this? Stu On Mar 4, 2011, at 9:29 AM, francesco wrote: > I use GRASS quite a lot, but always thought that it would be slow on vector > points. I know Brovelli and her team developed some modules, I'll check on > that. Good idea to use LibLAS as "driver" to turn LAS to xyz. > Francesco > > Il 04/03/2011 15:05, Stuart Edwards ha scritto: >> >> GRASS GIS (open source) has several modules for processing raw LiDAR data >> and the ability to script your own classification routines. LibLAS does a >> nice job of preprocessing (decoding) the LAS files so they can be input to >> GRASS as x,y,z or general ASCII format .......see: >> >> http://grass.osgeo.org/wiki/LIDAR#Micro-tutorial >> Stu >> >> >> On Mar 4, 2011, at 1:31 AM, francesco wrote: >> >>> Hello List, >>> I just registered, hello to everyone. >>> Regarding Aaron's question, I am playing around with LibLAS to develop a >>> ground classification procedure. It uses Axellson's progressive >>> triangulation of local minimum points - but I am also looking at other >>> solutions. Does anyone have other interesting approaches in mind? >>> Cheers, >>> Francesco >>> -- >>> ************************************************** >>> Francesco Pirotti >>> Dep. TESAF >>> CIRGEO – Interdepartmental Research Center on Cartography Photogrammetry >>> Remote Sensing and G.I.S. >>> University of Padova >>> Web: http://www.cirgeo.unipd.it/cirgeo/francescopirotti.htm >>> Email: [email protected] >>> Phone: +39 049 827 2710 >>> Phone: +39 349 55 39 261 >>> ************************************************** >>> >>> >>> Il 04/03/2011 00:49, Aaron Reyna ha scritto: >>>> >>>> Ah yes, >>>> >>>> I'll try the MCC-LiDAR. Great, thanks for the suggestion! >>>> >>>> Aaron >>>> >>>> On Thu, Mar 3, 2011 at 3:09 PM, Peter Tittmann <[email protected]> >>>> wrote: >>>> I've used MCC-Lidar http://sourceforge.net/apps/trac/mcclidar/ a little >>>> with marginal results. Not a great answer but something. TeraScan >>>> http://www.terrasolid.fi/en/products/terrascan is the elephant in that >>>> room. >>>> >>>> Peter >>>> >>>> >>>> On 03/03/2011 02:43 PM, Aaron Reyna wrote: >>>>> This may be too broad of a question, but has anyone seen or heard of a >>>>> way to do efficient ground modeling with libLAS? That is, take raw LiDAR >>>>> files (all default points) and model out the ground class? I do have raw >>>>> LiDAR files if it helps. >>>>> >>>>> Just throwing it out there. >>>>> >>>>> Best, >>>>> >>>>> Aaron >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Liblas-devel mailing list >>>>> [email protected] >>>>> http://lists.osgeo.org/mailman/listinfo/liblas-devel >>>> >>>> -- >>>> Peter Tittmann >>>> Geography Graduate Group >>>> UC Davis >>>> c. 707 849 4135 >>>> >>>> >>>> _______________________________________________ >>>> Liblas-devel mailing list >>>> [email protected] >>>> http://lists.osgeo.org/mailman/listinfo/liblas-devel >>> >>> >>> _______________________________________________ >>> Liblas-devel mailing list >>> [email protected] >>> http://lists.osgeo.org/mailman/listinfo/liblas-devel >> > > > -- > ************************************************** > Francesco Pirotti > Dep. TESAF > CIRGEO – Interdepartmental Research Center on Cartography Photogrammetry > Remote Sensing and G.I.S. > University of Padova > Web: http://www.cirgeo.unipd.it/cirgeo/francescopirotti.htm > Email: [email protected] > Phone: +39 049 827 2710 > Phone: +39 349 55 39 261 > ************************************************** > _______________________________________________ > Liblas-devel mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/liblas-devel
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