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<div>Thank you very much to both Markus! </div><div>bianca </div><div><br></div><div id="composer_signature"><div style="font-size:85%;color:#575757">Inviato dal mio dispositivo Samsung</div></div><br><br>-------- Messaggio originale --------<br>Da: Markus Neteler <neteler@osgeo.org> <br>Data: 30/03/2017 22:11 (GMT+01:00) <br>A: Markus Metz <markus.metz.giswork@gmail.com> <br>Cc: Bianca Federici <bianca.federici@unige.it>, grass-user <grass-user@lists.osgeo.org> <br>Oggetto: Re: [GRASS-user] Problems with r.surf.contour <br><br>Dear Bianca,<br><br>On Thu, Mar 30, 2017 at 5:27 PM, Markus Metz<br><markus.metz.giswork@gmail.com> wrote:<br>> On Thu, Mar 30, 2017 at 3:48 PM, Bianca Federici <bianca.federici@unige.it><br>...<br>>> The contour lines are quite coarse, and I can surely try to use other<br>>> interpolation methods... but the point is:<br>>> r.surf.contour works well???<br>><br>> I don't think so.<br><br>Yes, there are much better methods than r.surf.contour.<br><br>See also here:<br>https://grasswiki.osgeo.org/wiki/Contour_lines_to_DEM<br><br>markusN<br><br>>> it's seems to me that no linear interpolation between two contour levels<br>>> is perfomed, in fact the slope is not constant between them but increase<br>>> until half the distance and then decrease, or viceversa, instead of being<br>>> constant.<br>><br>> There are indeed strange patterns in the slope values between contour lines.<br>> The used distance to the second contour is not the shortest distance to the<br>> second contour, that is a bug. The distance calculation is unusual, it is<br>> not euclidean and not manhattan distance, no idea what kind of distance this<br>> is.<br>><br>> Apart from that, I would not use linear interpolation to create a surface<br>> from contour lines but use one of the previously mentioned r.resamp.*<br>> modules. And r.surf.contour is incredibly slow.<br>><br>> Markus M<br></body></html>