[GRASS-user] From pointcloud to dem - help

Markus Metz markus.metz.giswork at googlemail.com
Wed Jan 12 09:29:41 EST 2011

On Wed, Jan 12, 2011 at 2:17 PM, Jorn Anke <jornanke at hotmail.com> wrote:
> Dear Grass users,
> I have a pointcloud form PMVS
> (http://grail.cs.washington.edu/software/pmvs/) consisting of near to 6
> million points.
> The pointclouddata is georeferenced into world-coordinates (EUREF-89), and
> stored in a text file with the following format: X Y Z R G B. (RGB colordata
> can be deleted if required).
> What I want to do is to import the pointcloud into Grass 7.0, and to
> generate a surface modell/ dem, and to export the dem to a common
> file-format, e.g. ESRI SHP or Land-XML.
> I am quite new to Grass, so I would very much appreciate a brief description
> of the steps I will need to go through in order to obtain this.
First, import the point cloud with v.in.ascii. You can then filter the
points with the lidar tools to remove outliers (v.outlier) and obtain
a digital terrain model and a digital surface model
(v.lidar.edgedetection, v.lidar.growing, v.lidar.correction). The
v.surf.* modules can create a (raster) DEM by interpolating the
points. GRASS prefers raster maps for surface/terrain representation;
that also means that ESRI SHP or Land-XML being vector formats are not
really appropriate for a DEM. Common raster formats are e.g. GeoTIFF,
Erdas Imagine, or ESRI .hdr [1].

Markus M

[1] http://www.gdal.org/formats_list.html

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