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