[GRASS-dev] lidar tools update in grass7
Markus Metz
markus.metz.giswork at googlemail.com
Fri Feb 5 13:52:50 EST 2010
details on r40831:
Performance has been increased for all modules by reducing the default
segment size, interpolation settings are not affected. Previously, the
modules seemed to be optimized for settings where only one segment was
needed. As soon as several segments where needed, processing time
increased drastically. Fixed for all modules, now optimized for larger
datasets.
Sometimes interpolation settings were modified for the last row and
column segments, i.e. for these segments different interpolation
settings were used than for the other segments. The same spline step
values are now used for all segments.
All modules have a new flag to estimate point density and mean distance
between points. This mean distance is the minimum spline step, according
to the documentation recommended spline steps are 2 to 4 times the mean
distance, depending on the module.
All modules now create a proper name for the auxiliar table, sometimes a
name was created but a different one was used or a fully qualified name
with @ was used: illegal table name.
Several modules had memory leaks when accessing the auxiliar table, all
are fixed.
v.lidar.edgedetection assigned category 0 instead of 3 to unknown points
(neither edge nor terrain), fixed. There was a bad memory leak in
v.lidar.edgedetection, fixed.
v.outlier could not properly detect outliers if several segments were
needed, the points falling into the overlapping zones were not properly
updated (uninitialized variable used).
v.surf.bspline no longer produces artifacts along region boundaries and
is now optimized for larger datasets. AFAICT it did not properly work if
the region had to be subdivided into several segments, it was restricted
to one segment.
test environment was nc_spm_08
g.region vect=elev_lid792_bepts at PERMANENT res=1
north: 221230
south: 219580
west: 637740
east: 639530
nsres: 1
ewres: 1
rows: 1650
cols: 1790
cells: 2953500
e.g. for grass64
v.outlier --o --v input=elev_lid792_bepts at PERMANENT
output=elev_lid792_bepts_nooutliers64
outlier=elev_lid792_bepts_outliers64 soe=5 son=5 thres_o=0.1
and grass7
v.outlier --o --v input=elev_lid792_bepts at PERMANENT
output=elev_lid792_bepts_nooutliers outlier=elev_lid792_bepts_outliers
soe=5 son=5 thres_o=0.1
these settings will detect more outliers than are probably there, they
are for illustration of the artefacts.
obvious artefacts in elev_lid792_bepts_outliers64
or in grass64
v.surf.bspline --o --v input=elev_lid792_bepts at PERMANENT
raster=elev_lid792_rast64 sie=5 sin=5 type=bicubic lambda_i=0.1
vs. grass7
v.surf.bspline --o --v input=elev_lid792_bepts at PERMANENT
raster=elev_lid792_rast sie=5 sin=5 type=bicubic lambda_i=0.1
no more artefacts along the region boundaries and faster
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