#1480: v.outlier - distinguish positive and negative outlier filtering from
lidar
point clouds
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Reporter: sbl | Owner: grass-dev@…
Type: enhancement | Status: new
Priority: normal | Milestone:
Component: Vector | Version: svn-trunk
Keywords: review | Platform: Unspecified
Cpu: Unspecified |
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In forest areas LIDAR returns usually both: signals from tree-tops
(canopy) and from the ground as well. Unfortunately v.outlier (as it is
today) filters positive and negative outliers at the same time, because it
filters based on the absolute value of deviation from an interpolated
surface. In forest areas, this appoarch affects both ground- and canopy-
returns (meaning that very often both are being removed).[[BR]]
Usually a local minimum filtering is applied for removing vegetation
returns from LIDAR point clouds (see:
[http://www2.geog.ucl.ac.uk/~plewis/lidarforvegetation/UCL-ALS-
Lidar_for_Vegetation_Applications_2010.pdf] or
[http://www.fs.fed.us/rm/pubs_other/rmrs_2007_evans_j001.pdf]).[[BR]]
This is why I propose a p- and a n-flag for v.outlier, in order to be able
to specify, that only positive or negative outliers are filtered. The
attached code did the job for me. The attached two images illustrate my
result when applying my modified version of v.outlier to my data
rereatedly (similar to
[http://www.fs.fed.us/rm/pubs_other/rmrs_2007_evans_j001.pdf]). On is a
shaded relief of the DSM and the other a shaded relief of the DTM of the
same region (after removing positive outliers).
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Ticket URL: <http://trac.osgeo.org/grass/ticket/1480>
GRASS GIS <http://grass.osgeo.org>
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