<div dir="ltr">Bob,<div>I've had a fair amount of success directly generating rasters from the z values from LAS files of 3.3 billion points each using GRASS7 complied with liblas and the r.in.lidar, <a href="http://grass.osgeo.org/grass70/manuals/r.in.lidar.html">http://grass.osgeo.org/grass70/manuals/r.in.lidar.html</a> command. </div>
<div><br></div><div>As Remi mentioned, it can be quite memory intensive, <a href="http://www.ncgisconference.com/2013/documents/pdfs/Newcomb_Fri_1030.pdf">http://www.ncgisconference.com/2013/documents/pdfs/Newcomb_Fri_1030.pdf</a> . Point counts and Range calculations are fairly cheap, but skewness analysis can take a LOT of memory. For the 3.3 billion point data sets on partial coverage of a 753 million cell raster and limiting the amount of map in memory that was processed at one time to 15%, it still took 20GB of RAM to process for a skewness analysis. The extent of the raster created was much larger than the area covered by points, so that probably made some difference. Only processing an area for which there are points might cut down on the memory requirements somewhat.</div>
<div><br></div><div>Doug</div><div> </div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Oct 21, 2013 at 4:52 AM, Rémi Cura <span dir="ltr"><<a href="mailto:remi.cura@gmail.com" target="_blank">remi.cura@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>Hey,<br></div><div>I'm not M.Ramsey, I'm just a pointcloud user.</div><br>1. : you can "colorize" based on any attributes of points. Traditional point cloud softwares expect usually R G B attributes, but for some you can choose which attributes to use for coloring (CloudCompare).<br>
<br></div>2 : We have thought about visualisation (in this area it's about Level Of Details). The best we tried (because of lack of time) is to make another PC_Explode so it returns only a certain number of points per patch.<br>
<div><br></div><div>The next step is to writte points in patch following a quad tree structure (not deep first but breadth-first) (maybe using <a href="http://www.postgresql.org/docs/9.3/static/spgist-examples.html" target="_blank">http://www.postgresql.org/docs/9.3/static/spgist-examples.html</a> , not sure about this).</div>
<div>This way when taking only the first XX points in patches, you ensure these points are always well distributed in the patch.</div><div><br></div><div>This is the best we thought of without duplicating data (not an option with so big data anyway).</div>
<div><br></div><div>3 : about générating a raster from pointcloud :</div><div>You can do it in QGis , Grass Gis, or using GDAL or LasTool. (also in CloudCompare) Usually you have access to sophisticated interpolation methods (square inverse distance, etc etc). It is a hard problem in practice because of memory limitation and possible multiple holes in data.<br>
<br><br>Please feel free to ask if you want more details.<br><br>Cheers,</div><div><br></div><div>Rémi-C</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">2013/10/18 Basques, Bob (CI-StPaul) <span dir="ltr"><<a href="mailto:bob.basques@ci.stpaul.mn.us" target="_blank">bob.basques@ci.stpaul.mn.us</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5">
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<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS"">Hi all,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS""><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS"">Juat watched Paul Ramseys video on point cloud storage and it made me think of a few questions to ask.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS""><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS"">Quesitions:<u></u><u></u></span></p>
<p><u></u><span style="font-size:8.0pt;font-family:Symbol"><span>ˇ<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:8.0pt;font-family:"Comic Sans MS"">Sort of a DB processing question, probably not thought about yet, but can the pointcloud be colorized based on a raster/vector of view passed in? As in aerial photos obviously,
but less obvious would be for oblique photos. <u></u><u></u></span></p>
<p><u></u><span style="font-size:8.0pt;font-family:Symbol"><span>ˇ<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:8.0pt;font-family:"Comic Sans MS"">Generalizing of the pointclouds, from my perspective to be used for zoom in/out processes for visualization. Could a average height based on a (pyramid) tiling possibly
be used to get close to a generalizing scheme, I know this approach might offend purists as far as data integrity . .<u></u><u></u></span></p>
<p><u></u><span style="font-size:8.0pt;font-family:Symbol"><span>ˇ<span style="font:7.0pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:8.0pt;font-family:"Comic Sans MS"">There was a question in the video that I watched related to building a surface grid from the pointcloud, I wonder about a simple tile averaging as a method for generating
a grid. Anyone tried and have available some benchmarks for this idea?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS""><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS"">Thanks<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS""><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS"">Bobb<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS""><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Comic Sans MS""><u></u> <u></u></span></p>
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