Hello list:
I've been working recently with v.vol.rst and I have doubts about
the real function of the parameter "zmult": the manual says it allows
the user to re-scale (change units of) the z coordinates of the data; but
I obtain better results when using high values (about 20) of zmult even if no unit
transformation (re-scaling) is needed at all (all data in metres). Could anyone give me a
hint on the actual role of zmult in the interpolation process? Is it reasonable to use "very"
high values (e.g. 100)?
Thank you very much
On Fri, Oct 3, 2008 at 9:27 AM, Eduardo corbelle
<eduardo.corbelle@gmail.com> wrote:
Hello list:
I've been working recently with v.vol.rst and I have doubts about
the real function of the parameter "zmult": the manual says it allows
the user to re-scale (change units of) the z coordinates of the data; but
I obtain better results when using high values (about 20) of zmult even if
no unit transformation (re-scaling) is needed at all (all data in metres). Could
anyone give me a
hint on the actual role of zmult in the interpolation process? Is it
reasonable to use "very" high values (e.g. 100)?
Helena once told me:
Rescaling of z-coordinates is for example needed when the distances in
vertical direction are much smaller than the horizontal distances, if
that is the case, the value of zmult should be selected so that the
vertical and horizontal distances have about the same magnitude.
Might this help as explanation?
Markus
Thank you Markus.
That makes sense for me, I have horizontal distances between points of around 1-2 km, and vertical distances range between 10-20 m. Further trials with “v.vol.rst -c” showed better results for zmult=50-100, getting worse both for higher and lower values of zmult.
Regards
Eduardo
2008/10/6 Markus Neteler <neteler@osgeo.org>
On Fri, Oct 3, 2008 at 9:27 AM, Eduardo corbelle
<eduardo.corbelle@gmail.com> wrote:
Hello list:
I’ve been working recently with v.vol.rst and I have doubts about
the real function of the parameter “zmult”: the manual says it allows
the user to re-scale (change units of) the z coordinates of the data; but
I obtain better results when using high values (about 20) of zmult even if
no unit transformation (re-scaling) is needed at all (all data in metres). Could
anyone give me a
hint on the actual role of zmult in the interpolation process? Is it
reasonable to use “very” high values (e.g. 100)?
Helena once told me:
Rescaling of z-coordinates is for example needed when the distances in
vertical direction are much smaller than the horizontal distances, if
that is the case, the value of zmult should be selected so that the
vertical and horizontal distances have about the same magnitude.
Might this help as explanation?
Markus