It just came to me: if I have a vector map to be interpolated by RST,
how does the algorithm chooses between points that are very close to
each other?
And if I have more than one point with the same coordinates, but
different values?
thks all
Carlos
--
+-----------------------------------------------------------+
Carlos Henrique Grohmann - Guano
Geologist M.Sc - Doctorate Student at IGc-USP - Brazil
Linux User #89721 - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+
_________________
"Good morning, doctors. I have taken the liberty of removing Windows
95 from my hard drive."
--The winning entry in a "What were HAL's first words" contest judged
by 2001: A SPACE ODYSSEY creator Arthur C. Clarke
I cant answer the question of how the v.surf.rst module choses points,
but I can say that with the use of r.in.xyz you can control this quite
well.
For example, (and relating to the last question) you can use different
methods to assign values to the cells from ASCII import. Meaning if
you have multiple points in a cell, and you only want the values that
are the minimum in the cell, use the 'method=min' option.
Alternatively, you can use 'mean' and 'max' for other applications as
well.
then you would r.to.vect the data, as 3d points and then interpolate
with v.surf.rst. If I recall right, by doing this r.in.xyz, it cut
out about 35% of the processing time for v.surf.rst in my application.
Especially for LiDAR data, I found the r.in.xyz module to be nothing
short of spectacular. With the 'method=n' option, and an r.report
<raster> unit=p, you can see the percent distribution of points per
cell to help set cell size. These are some great tools!
Mark
On 5/27/08, Carlos Guâno Grohmann <carlos.grohmann@gmail.com> wrote:
It just came to me: if I have a vector map to be interpolated by RST,
how does the algorithm chooses between points that are very close to
each other?
And if I have more than one point with the same coordinates, but
different values?
thks all
Carlos
--
+-----------------------------------------------------------+
Carlos Henrique Grohmann - Guano
Geologist M.Sc - Doctorate Student at IGc-USP - Brazil
Linux User #89721 - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+
_________________
"Good morning, doctors. I have taken the liberty of removing Windows
95 from my hard drive."
--The winning entry in a "What were HAL's first words" contest judged
by 2001: A SPACE ODYSSEY creator Arthur C. Clarke
first point found at a given location is preserved and any consequent
points within distance smaller than dmin are ignored (the z-values are
not taken into account). I have done some experiments with 3D distance as
well if you need to take into account the z - it is very easy to change
that in the code but that would require adding a flag and I am not sure
that many users would need it.
If your data are contours, use v.generalize to "thin" the points first -
it speeds up the processing a lot and the results are much better - see
here: http://skagit.meas.ncsu.edu/~helena/grasswork/interpgen.html
If you want to use mean value of your close points - the best approach is
through r.in.xyz - see the example in its man page
Helena
cheers
On Wed, May 28, 2008 at 5:19 AM, Markus Neteler <neteler@osgeo.org> wrote:
Maybe best ask to Helena who is on the road and not subscribed
to this list AFAIK...
please post the answer then!
markus
On Tue, May 27, 2008 at 9:39 PM, Carlos Guâno Grohmann
<carlos.grohmann@gmail.com> wrote:
It just came to me: if I have a vector map to be interpolated by RST,
how does the algorithm chooses between points that are very close to
each other?
And if I have more than one point with the same coordinates, but
different values?
thks all
Carlos
--
+-----------------------------------------------------------+
Carlos Henrique Grohmann - Guano
Geologist M.Sc - Doctorate Student at IGc-USP - Brazil
Linux User #89721 - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+
_________________
"Good morning, doctors. I have taken the liberty of removing Windows
95 from my hard drive."
--The winning entry in a "What were HAL's first words" contest judged
by 2001: A SPACE ODYSSEY creator Arthur C. Clarke
--
+-----------------------------------------------------------+
Carlos Henrique Grohmann - Guano
Geologist M.Sc - Doctorate Student at IGc-USP - Brazil
Linux User #89721 - carlos dot grohmann at gmail dot com
+-----------------------------------------------------------+
_________________
"Good morning, doctors. I have taken the liberty of removing Windows
95 from my hard drive."
--The winning entry in a "What were HAL's first words" contest judged
by 2001: A SPACE ODYSSEY creator Arthur C. Clarke