<div dir="ltr">Hi,<div><br></div><div>I believe that Alex talks about the HAG stored as an additional point atttribute to an "Extra Bytes" field via the '-store_as_extra_bytes' switch.</div><div><br></div><div><a href="http://lastools.org/download/lasheight_README.txt">http://lastools.org/download/lasheight_README.txt</a></div><div><br></div><div>There was a discussion on this in the LAStools user forum whether cm resolution with a scale factor of 0.01 and a 16 bits signed integer storage are enough for most trees.</div><div><br></div><div><a href="http://groups.google.com/forum/#!searchin/lastools/lasheight$20store_as_extra_bytes">http://groups.google.com/forum/#!searchin/lastools/lasheight$20store_as_extra_bytes</a><br></div><div><br></div><div>"Extra Bytes" fields are described in the LAS 1.4 specification and are therefore also more and more readable in other software.<br></div><div><br></div><div>Regards from Brazil,</div><div><br></div><div>Martin @rapidlasso</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Nov 9, 2016 at 9:12 PM, Van Dyke, Daryl <span dir="ltr"><<a href="mailto:daryl_van_dyke@fws.gov" target="_blank">daryl_van_dyke@fws.gov</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">LAStools IIRC encodes the non-standard HAG field into the 'user bytes' portion of the LAS file. It's special-sauce approach to encoding that information into a user-expandable portion of the LAS standard.<div><br></div><div>To keep in mind: the HAG field (again, IIRC) is based on an internal integer representation - it quantizes the data into the binned integers to store them. You want to ensure the resolution of the storage is appropriate for your application (though for most tree sizes, in most units, it's probably fine). <div><br></div><div>I don't think you'll find any tools outside of LASTools that support that feature. You may also not be aware that the 'free' or non-licensed version of LASTools imposes noise on output.</div><div><br>Daryl</div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Nov 9, 2016 at 12:00 PM, <span dir="ltr"><<a href="mailto:liblas-devel-request@lists.osgeo.org" target="_blank">liblas-devel-request@lists.<wbr>osgeo.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Send Liblas-devel mailing list submissions to<br>
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<br>Today's Topics:<br>
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1. libLAS and HEIGHT_ABOVE_GROUND attribute (Alexandre Guyot)<br>
<br><br>---------- Forwarded message ----------<br>From: Alexandre Guyot <<a href="mailto:alexguyot@yahoo.fr" target="_blank">alexguyot@yahoo.fr</a>><br>To: "<a href="mailto:liblas-devel@lists.osgeo.org" target="_blank">liblas-devel@lists.osgeo.<wbr>org</a>" <<a href="mailto:liblas-devel@lists.osgeo.org" target="_blank">liblas-devel@lists.osgeo.org</a>><br>Cc: <br>Date: Tue, 8 Nov 2016 21:00:17 +0000<br>Subject: [Liblas-devel] libLAS and HEIGHT_ABOVE_GROUND attribute<br><div><div style="color:#000;background-color:#fff;font-family:verdana,helvetica,sans-serif;font-size:13px"><div id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5208" dir="ltr"><span id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5393">Hi,<br id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5380"><br id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5381">I'm using the liblas python API to read through some LiDAR point clouds.<br id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5383">I can access all the standard point attributes of my dataset, however I can't figure out how to read the HEIGHT_ABOVE_GROUND value of my points.<br id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5384">This HEIGHT_ABOVE_GROUND attribute was computed in LAStools using "lasheight".</span></div><div dir="ltr" id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5438"><span id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5393">This attribute is readable on popular LiDAR viewers (GlobalMapper for instance) but I don't know how to reach it using libLAS.</span></div><br><div dir="ltr" id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5505"><span id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5393"><span id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5480"></span>Any ideas ?<br id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5390"><br id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5391">Thanks a lot,<br id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5392">Alex</span></div><div id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5209"> </div><div class="m_-4386984177042842137m_-8738692111892250383signature" id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5294"><div id="m_-4386984177042842137m_-8738692111892250383yui_3_16_0_ym19_1_1478638363984_5293"> </div></div></div></div><br>______________________________<wbr>_________________<br>
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