<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>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.</div><div><br></div>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. <div><br><div>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. </div><div><br></div><div> Has anyone else wrestled with this?</div><div><br></div><div>Stu<br><div><br></div><div><br><div><div>On Mar 4, 2011, at 9:29 AM, francesco wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
<div text="#000000" bgcolor="#ffffff">
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.<br>
Francesco<br>
<br>
Il 04/03/2011 15:05, Stuart Edwards ha scritto:
<blockquote cite="mid:A32113F3-B8E1-4165-86EF-F33D6824193F@cinci.rr.com" type="cite">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:
<div><br>
</div>
<div><span class="Apple-style-span" style="font-family: Times;">
<pre><a moz-do-not-send="true" href="http://grass.osgeo.org/wiki/LIDAR#Micro-tutorial">http://grass.osgeo.org/wiki/LIDAR#Micro-tutorial</a></pre>
</span>
<div>Stu</div>
<div><br>
</div>
<div><br>
</div>
<div>
<div>On Mar 4, 2011, at 1:31 AM, francesco wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<div text="#000000" bgcolor="#ffffff"> Hello List, <br>
I just registered, hello to everyone. <br>
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?<br>
Cheers,<br>
Francesco<br>
<div class="moz-signature">-- <br>
<font face="Arial, Helvetica, sans-serif" size="-1"> <small>**************************************************<br>
<b>Francesco Pirotti</b><br>
Dep. TESAF <br>
CIRGEO – Interdepartmental Research Center on
Cartography Photogrammetry <br>
Remote Sensing and G.I.S. <br>
University of Padova <br>
Web: <a moz-do-not-send="true" href="http://www.cirgeo.unipd.it/cirgeo/francescopirotti.htm">http://www.cirgeo.unipd.it/cirgeo/francescopirotti.htm</a><br>
Email: <a moz-do-not-send="true" href="mailto:francesco.pirotti@unipd.it">francesco.pirotti@unipd.it</a><br>
Phone: +39 049 827 2710 <br>
Phone: +39 349 55 39 261<br>
************************************************** </small>
</font></div>
<br>
<br>
Il 04/03/2011 00:49, Aaron Reyna ha scritto:
<blockquote cite="mid:AANLkTim1gpLmGvxi-28PWWWjTSvrqdRaBykCbsyAo0o3@mail.gmail.com" type="cite">Ah yes,
<div><br>
</div>
<div>I'll try the MCC-LiDAR. Great, thanks for the
suggestion!</div>
<div><br>
</div>
<div>Aaron <br>
<br>
<div class="gmail_quote">On Thu, Mar 3, 2011 at 3:09
PM, Peter Tittmann <span dir="ltr"><<a moz-do-not-send="true" href="mailto:pwtittmann@ucdavis.edu">pwtittmann@ucdavis.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt
0pt 0pt 0.8ex; border-left: 1px solid rgb(204,
204, 204); padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000"> I've used
MCC-Lidar <a moz-do-not-send="true" href="http://sourceforge.net/apps/trac/mcclidar/" target="_blank">http://sourceforge.net/apps/trac/mcclidar/</a>
a little with marginal results. Not a great
answer but something. TeraScan <a moz-do-not-send="true" href="http://www.terrasolid.fi/en/products/terrascan" target="_blank">http://www.terrasolid.fi/en/products/terrascan</a>
is the elephant in that room.<br>
<br>
Peter
<div>
<div class="h5"><br>
<br>
On 03/03/2011 02:43 PM, Aaron Reyna wrote: </div>
</div>
<blockquote type="cite">
<div>
<div class="h5">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.
<div> <br>
</div>
<div>Just throwing it out there.</div>
<div><br>
</div>
<div>Best,</div>
<div><br>
</div>
<div>Aaron
<div><br>
</div>
<div><br>
</div>
</div>
</div>
</div>
<pre><fieldset></fieldset>
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</pre>
</blockquote>
<br>
<pre cols="72">--
Peter Tittmann
Geography Graduate Group
UC Davis
c. 707 849 4135</pre>
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</blockquote>
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<div class="moz-signature">-- <br>
<font face="Arial, Helvetica, sans-serif" size="-1">
**************************************************<br>
<b>Francesco Pirotti</b> <br>
Dep. TESAF <br>
CIRGEO – Interdepartmental Research Center on Cartography
Photogrammetry <br>
Remote Sensing and G.I.S. <br>
University of Padova <br>
Web: <a href="http://www.cirgeo.unipd.it/cirgeo/francescopirotti.htm">http://www.cirgeo.unipd.it/cirgeo/francescopirotti.htm</a>
<br>
Email: <a href="mailto:francesco.pirotti@unipd.it">francesco.pirotti@unipd.it</a>
<br>
Phone: +39 049 827 2710 <br>
Phone: +39 349 55 39 261<br>
**************************************************
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