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<p>Dear Markus, <br>
</p>
<p>thank you very much for your suggestion... I never used the
option -a in g.region command!</p>
<p>The results improved a lot, but some problems are still present
in the linear interpolation between two contour levels.</p>
<p>Here you may see the slope map and a slope profile that enhance
the not proper result:</p>
<p><a class="moz-txt-link-freetext" href="https://www.dropbox.com/s/7olimii9s0m21rh/slope_contourlevel.PNG?dl=0">https://www.dropbox.com/s/7olimii9s0m21rh/slope_contourlevel.PNG?dl=0</a><br>
</p>
<p>I hope that you or somebody else have other suggestions ;-)</p>
<p> Bianca </p>
<br>
<div class="moz-cite-prefix">Il 27/03/2017 21:21, Markus Metz ha
scritto:<br>
</div>
<blockquote
cite="mid:CAG+h=FFLpF_JbWDayNMXEoK+9VsJgTJ7VxQS7wi5MoqD78LQSg@mail.gmail.com"
type="cite">
<div dir="ltr">g.region is a very powerful tool with sometimes
unexpected effects. See suggested workflow below.<br>
<div><br>
On Mon, Mar 27, 2017 at 12:26 PM, Bianca Federici <<a
moz-do-not-send="true"
href="mailto:bianca.federici@unige.it">bianca.federici@unige.it</a>>
wrote:<br>
><br>
> Dear all,<br>
> I'm writing to report a problem I noticed using
r.surf.contour.<br>
> I created a DTM from contour lines, but I notice
something a wrong behaviour of the r.surf.contour resulting
map.<br>
><br>
> In detail I imported with v.in.ogr a shape file
describing contour lines every 25m of altitude<br>
> Then, I converted in raster (setting a resolution of the
computational region equal to 1m), and created the DTM (
setting a resolution of the computational region equal to 5m)
with r.surf.contour.<br>
> Either plotting a profile of the DTM and creating the
slope map (with r.slope.aspect), it's evident that
r.surf.contour works bad.<br>
><br>
> Here you can see the slope map, with the contour level in
black, and the position of the extracted cross section; you
may notice artificial steps mainly in corrispondence of the
contour levels, instead of uniform slopes:<br>
> <a moz-do-not-send="true"
href="https://www.dropbox.com/s/7olimii9s0m21rh/slope_contourlevel.PNG?dl=0">https://www.dropbox.com/s/7olimii9s0m21rh/slope_contourlevel.PNG?dl=0</a><br>
> Here you can see the DTM profile along the cross section,
that shows the irregular morphology of the created DTM<br>
> <a moz-do-not-send="true"
href="https://www.dropbox.com/s/useoxstmceyulk6/DTM_cross_section.PNG?dl=0">https://www.dropbox.com/s/useoxstmceyulk6/DTM_cross_section.PNG?dl=0</a><br>
><br>
> I tested it in GRASS 6.4.4, 7.0.3 and 7.2.0, working
either in Windows and in Linux.<br>
><br>
> I hope that the developers team could correct this
malfunction.<br>
> Best regards,<br>
> Bianca<br>
><br>
> PS: The used commands:<br>
> v.in.ogr ...<br>
> g.region -p res=1<br>
> v.to.rast input=contourlevel25m type=line
output=contourlevel25m use=attr column=ELEVATION<br>
> g.region -p res=5<br>
> r.surf.contour input=contourlevel25m
output=dtm_contourlevel25m<br>
> r.slope.aspect elevation=dtm_contourlevel25m
slope=slope_contourlevel25m<br>
<br>
</div>
<div>Please try<br>
</div>
<div>v.in.ogr ...<br>
</div>
<div>g.region -p -a res=5 vect=contourlevel25m</div>
<div>v.to.rast ...<br>
<br>
</div>
<div># do not change the region again<br>
</div>
<div>r.surf.contour ...<br>
<br>
</div>
<div>HTH,<br>
<br>
</div>
<div>Markus M<br>
</div>
<div><br>
</div>
<div><br>
><br>
> --<br>
> Eng. Bianca Federici, PhD<br>
> Assistant Professor in Geomatics<br>
><br>
> DICCA - Department of Civil, Chemical and Environmental
Engineering<br>
> Laboratory of Geodesy, Geomatics and GIS<br>
> University of Genoa<br>
> Via Montallegro, 1 - 16145 Genova ITALY<br>
> Phone: +39 010 353 2421 - Fax: +39 010 353 2546<br>
> <a moz-do-not-send="true"
href="mailto:E-mail%3Abianca.federici@unige.it">E-mail:bianca.federici@unige.it</a>
-<a moz-do-not-send="true"
href="http://www.dicca.unige.it/geomatica/ricerca">www.dicca.unige.it/geomatica/ricerca</a><br>
><br>
> Gter srl Innovation in Geomatics, Gnss and Gis<br>
> Spin-off of the University of Genoa<br>
> Piazza De Marini 3/61, 16123 Genova<br>
> Phone: +39 010 8694830 - Fax: +39 010 8694737 -<br>
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