[GRASS-user] From pointcloud to dem - help

[Markus Metz]

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