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? Thanks Daniel On Mar 30, 2012 6:47 AM, "Daniel Lee" <[email protected]> wrote:
> Hi there, > > 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? > > Best, > Daniel > > -- > > B.Sc. Daniel Lee > Geschäftsführung für Forschung und Entwicklung > ISIS - International Solar Information Solutions GbR > Vertreten durch: Daniel Lee, Nepomuk Reinhard und Nils Räder > > Deutschhausstr. 10 > 35037 Marburg > Festnetz: +49 6421 379 6256 > Mobil: +49 176 6127 7269 > E-Mail: [email protected] > Web: http://www.isi-solutions.org > > 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. > Zusätzliche Unterstützung erhält ISIS von dem Entrepreneurship Cluster > Mittelhessen, der Universität Marburg, dem Laboratory for Climatology and > Remote Sensing und dem GIS-Lab Marburg. > > > > > Am 29. März 2012 22:59 schrieb Daniel Victoria <[email protected]> > : > >> Hi all, >> >> I'm trying to calculate the height from the ground of several lidar >> points (15million) in order to get the number of points that occur at >> different height levels. I read some older posts about using r.in.xyz >> (or r.in.lidar in grass 7) but I could not understand how to count the >> number or points that have height from 0 to 5 m above the ground, for >> instance. So, I'm trying to do the following. >> >> 1) import points using v.in.lidar (Grass 7 ubuntu linux) >> 2) create a column in the database for the ground height and one for >> elevation >> 3) populate height column from ground raster (generate in another >> process) using v.what.rast >> 4) calculate elevation as zcoord - ground for each point (v.db.update) >> >> As you might imagine, this takes a long time. Just to import a 400Mb >> lidar file takes around 50min. >> Is there any easier way that I'm not envisioning? >> >> I'm running Grass 7 with liblas on a Ubuntu Virtual Machine and sqlite >> backend. >> >> Thanks >> Daniel >> _______________________________________________ >> grass-user mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/grass-user >> > >
_______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
