g.region is a very powerful tool with sometimes unexpected effects. See suggested workflow below.
On Mon, Mar 27, 2017 at 12:26 PM, Bianca Federici <[email protected]> wrote: > > Dear all, > I'm writing to report a problem I noticed using r.surf.contour. > I created a DTM from contour lines, but I notice something a wrong behaviour of the r.surf.contour resulting map. > > In detail I imported with v.in.ogr a shape file describing contour lines every 25m of altitude > 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. > 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. > > 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: > https://www.dropbox.com/s/7olimii9s0m21rh/slope_contourlevel.PNG?dl=0 > Here you can see the DTM profile along the cross section, that shows the irregular morphology of the created DTM > https://www.dropbox.com/s/useoxstmceyulk6/DTM_cross_section.PNG?dl=0 > > I tested it in GRASS 6.4.4, 7.0.3 and 7.2.0, working either in Windows and in Linux. > > I hope that the developers team could correct this malfunction. > Best regards, > Bianca > > PS: The used commands: > v.in.ogr ... > g.region -p res=1 > v.to.rast input=contourlevel25m type=line output=contourlevel25m use=attr column=ELEVATION > g.region -p res=5 > r.surf.contour input=contourlevel25m output=dtm_contourlevel25m > r.slope.aspect elevation=dtm_contourlevel25m slope=slope_contourlevel25m Please try v.in.ogr ... g.region -p -a res=5 vect=contourlevel25m v.to.rast ... # do not change the region again r.surf.contour ... HTH, Markus M > > -- > Eng. Bianca Federici, PhD > Assistant Professor in Geomatics > > DICCA - Department of Civil, Chemical and Environmental Engineering > Laboratory of Geodesy, Geomatics and GIS > University of Genoa > Via Montallegro, 1 - 16145 Genova ITALY > Phone: +39 010 353 2421 - Fax: +39 010 353 2546 > E-mail:[email protected] -www.dicca.unige.it/geomatica/ricerca > > Gter srl Innovation in Geomatics, Gnss and Gis > Spin-off of the University of Genoa > Piazza De Marini 3/61, 16123 Genova > Phone: +39 010 8694830 - Fax: +39 010 8694737 - > E-mail:[email protected] -www.gter.it > www.facebook.com/Gteronline > www.twitter.com/Gteronline > > ----------------------------------------------------------------- > Please consider the environment before printing this email! > > _______________________________________________ > grass-user mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/grass-user
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