[GRASS-user] Problems with r.surf.contour

[Bianca Federici]

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

-- 
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:bianca.federici at unige.it  -www.dicca.unige.it/geomatica/ricerca

Gter srl Innovation in Geomatics, Gnss and Gis
Spin-off of the University of Genoa
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