Hi Daniel,<br><br>You could try making different rasters with classes (0-5m over ground, 5-10m over ground, etc.) and then convert them into polygons, then check how many points are inside them. I'm not sure if it'd be faster than the way you suggested originally, though, when you think that you'd have to make the rasters first, etc.<br>
<br>I ended up giving up on large vector operations with LiDAR point clouds in GRASS 6.4 because it simply took way too long, but I was dealing with millions of points. For such a small dataset it's probably fine, since as long as you know your script is okay you can let it run through your lunch break ;)<br>
<br>Daniel<br clear="all">
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"><span style="font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"></span></p><p>--<br></p><p>B.Sc. Daniel Lee<br>
Geschäftsführung für Forschung und Entwicklung<br>ISIS - International Solar Information Solutions GbR<br>Vertreten durch: Daniel Lee, Nepomuk Reinhard und Nils Räder<br></p><p>Deutschhausstr. 10<br>35037 Marburg<br>Festnetz: <a value="+4964213796256" style="color:rgb(28,81,168)">+49 6421 379 6256</a><br>
Mobil: <a value="+4917661277269" style="color:rgb(28,81,168)">+49 176 6127 7269</a><br>E-Mail: <a href="mailto:Lee@isi-solutions.org" style="color:rgb(28,81,168)" target="_blank">Lee@isi-solutions.org</a><br>Web: <a href="http://www.isi-solutions.org/" style="color:rgb(28,81,168)" target="_blank">http://www.isi-solutions.org</a></p>
<p>ISIS wird gefördert durch die Bundesrepublik Deutschland, Zuwendungsgeber: Bundesministerium für Wirtschaft und Technologie aufgrund eines Beschlusses des Deutschen Bundestages, sowie durch die Europäische Union, Zuwendungsgeber: Europäischer Sozialfonds.<br>
Zusätzliche Unterstützung erhält ISIS von dem Entrepreneurship Cluster Mittelhessen, der Universität Marburg, dem Laboratory for Climatology and Remote Sensing und dem GIS-Lab Marburg.</p><p></p><br>
<br><br><div class="gmail_quote">Am 30. März 2012 13:00 schrieb Daniel Victoria <span dir="ltr"><<a href="mailto:daniel.victoria@gmail.com">daniel.victoria@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<p>I need to calculate the number of points at different height levels. That is, how many points are from 0 to 5 meters? And from 5 to 10? And so on. So I believe I need to work with vector points and a database. Or is there another way?<br>
Thanks<span class="HOEnZb"><font color="#888888"><br>
Daniel</font></span></p><div class="HOEnZb"><div class="h5">
<div class="gmail_quote">On Mar 30, 2012 6:47 AM, "Daniel Lee" <<a href="mailto:lee@isi-solutions.org" target="_blank">lee@isi-solutions.org</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi there,<br><br>I don't work too much with vectors, but my personal experience with them has been fairly slow, perhaps due to the topology. If you have access to the raw point cloud, you could try importing the ground and surface points as separate rasters using r.in.xyz and then use r.mapcalc to get the height by subtracting the ground from the surface raster. Or do you definitely need vector points as an output?<br>
<br>Best,<br>Daniel<br clear="all">
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"><span style="font-size:13px;font-family:arial,sans-serif"></span></p><p>--<br></p><p>B.Sc. Daniel Lee<br>
Geschäftsführung für Forschung und Entwicklung<br>ISIS - International Solar Information Solutions GbR<br>Vertreten durch: Daniel Lee, Nepomuk Reinhard und Nils Räder<br></p><p>Deutschhausstr. 10<br>35037 Marburg<br>Festnetz: <a value="+4964213796256" style="color:rgb(28,81,168)">+49 6421 379 6256</a><br>
Mobil: <a value="+4917661277269" style="color:rgb(28,81,168)">+49 176 6127 7269</a><br>E-Mail: <a href="mailto:Lee@isi-solutions.org" style="color:rgb(28,81,168)" target="_blank">Lee@isi-solutions.org</a><br>Web: <a href="http://www.isi-solutions.org/" style="color:rgb(28,81,168)" target="_blank">http://www.isi-solutions.org</a></p>
<p>ISIS wird gefördert durch die Bundesrepublik Deutschland, Zuwendungsgeber: Bundesministerium für Wirtschaft und Technologie aufgrund eines Beschlusses des Deutschen Bundestages, sowie durch die Europäische Union, Zuwendungsgeber: Europäischer Sozialfonds.<br>
Zusätzliche Unterstützung erhält ISIS von dem Entrepreneurship Cluster Mittelhessen, der Universität Marburg, dem Laboratory for Climatology and Remote Sensing und dem GIS-Lab Marburg.</p><p></p><br>
<br><br><div class="gmail_quote">Am 29. März 2012 22:59 schrieb Daniel Victoria <span dir="ltr"><<a href="mailto:daniel.victoria@gmail.com" target="_blank">daniel.victoria@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi all,<br>
<br>
I'm trying to calculate the height from the ground of several lidar<br>
points (15million) in order to get the number of points that occur at<br>
different height levels. I read some older posts about using r.in.xyz<br>
(or r.in.lidar in grass 7) but I could not understand how to count the<br>
number or points that have height from 0 to 5 m above the ground, for<br>
instance. So, I'm trying to do the following.<br>
<br>
1) import points using v.in.lidar (Grass 7 ubuntu linux)<br>
2) create a column in the database for the ground height and one for elevation<br>
3) populate height column from ground raster (generate in another<br>
process) using v.what.rast<br>
4) calculate elevation as zcoord - ground for each point (v.db.update)<br>
<br>
As you might imagine, this takes a long time. Just to import a 400Mb<br>
lidar file takes around 50min.<br>
Is there any easier way that I'm not envisioning?<br>
<br>
I'm running Grass 7 with liblas on a Ubuntu Virtual Machine and sqlite backend.<br>
<br>
Thanks<br>
Daniel<br>
_______________________________________________<br>
grass-user mailing list<br>
<a href="mailto:grass-user@lists.osgeo.org" target="_blank">grass-user@lists.osgeo.org</a><br>
<a href="http://lists.osgeo.org/mailman/listinfo/grass-user" target="_blank">http://lists.osgeo.org/mailman/listinfo/grass-user</a><br>
</blockquote></div><br>
</blockquote></div>
</div></div></blockquote></div><br>