so far, I have been masking either via MASK or r.mapcalc. This way, only cells corresponding to MASK would display in the masked raster.
In contrast, now I would like cells corresponding to a "mask" NOT to display* in the main raster layer. Is there a way to do it?
This is part of a larger issue I am addressing and that I will briefly describe. In the attached sample image, you see points imported via v.in.ascii and used to get the green interpolated raster. Values at black points are greater than zero, whereas the value of the white point is zero (and it is not used for interpolation since it has no biological meaning).
The end result would be to clip out a portion of the green raster around the white point. This portion would be delimited by midpoints between the white point and the closest neighboring black points.
So far, I have been trying to get a vector buffer around the white point and then v.to.rast for some kind of subsequent clipping (described above*). However I have no cue on how to get a comlex shape from neighboring points as described. Is there a method already in place to do this?
Many thanks in advance and any hints much appreciated,
Luigi
grass6/cygwin user
INFINITO ADSLFLAT 4 MEGA: SOLO 27,90 EURO AL MESE IVA INCLUSA IP STATICO, BANDA GARANTITA 256Kbps ANTIVIRUS E FIREWALL INCLUSI NEL PREZZO
Il giorno mar, 04/04/2006 alle 19.50 +0200, lponti@infinito.it ha
scritto:
The end result would be to clip out a portion of the green
raster around the white point. This portion would be
delimited by midpoints between the white point and the
closest neighboring black points.
Not sure it would fit, but did you give a look at v.voronoi ?
HTH, Steko
--
Stefano Costa http://www.iosa.it Software Open Source per l'Archeologia
Jabber: steko@jabber.linux.it
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Linux Registered User #385969 counter.li.org
If white == 1 and black == 0 and you want all the "green" area
half-way between the white point and the black point, why don't you
try selecting all areas "green" >= 0.5?
Alternatively, you could buffer the white points by some reasonable
distance and select for all cells within X meters of the white point.
David
On 4/4/06, lponti@infinito.it <lponti@infinito.it> wrote:
Dear list,
so far, I have been masking either via MASK or r.mapcalc.
This way, only cells corresponding to MASK would display
in the masked raster.
In contrast, now I would like cells corresponding to a
"mask" NOT to display* in the main raster layer. Is there
a way to do it?
This is part of a larger issue I am addressing and that I
will briefly describe. In the attached sample image, you
see points imported via v.in.ascii and used to get the
green interpolated raster. Values at black points are
greater than zero, whereas the value of the white point is
zero (and it is not used for interpolation since it has no
biological meaning).
The end result would be to clip out a portion of the green
raster around the white point. This portion would be
delimited by midpoints between the white point and the
closest neighboring black points.
So far, I have been trying to get a vector buffer around
the white point and then v.to.rast for some kind of
subsequent clipping (described above*). However I have no
cue on how to get a comlex shape from neighboring points
as described. Is there a method already in place to do
this?
Many thanks in advance and any hints much appreciated,
Luigi
grass6/cygwin user
INFINITO ADSLFLAT 4 MEGA: SOLO 27,90 EURO AL MESE IVA INCLUSA IP STATICO, BANDA GARANTITA 256Kbps ANTIVIRUS E FIREWALL INCLUSI NEL PREZZO
Thanks David:
Your idea is something I had not thought to. The more I use GRASS, the better I appreciate r.mapcalc.
Thanks again Stefano:
I looked at v.voronoi and it seems to get exactly the buffer area I wanted. Voronoi polygons are also an interesting geometric concept that I did not know about.
If white == 1 and black == 0 and you want all the "green" area
half-way between the white point and the black point, why don't you
try selecting all areas "green" >= 0.5?
Alternatively, you could buffer the white points by some reasonable
distance and select for all cells within X meters of the white point.
David
On 4/4/06, lponti@infinito.it <lponti@infinito.it> wrote:
Dear list,
so far, I have been masking either via MASK or r.mapcalc.
This way, only cells corresponding to MASK would display
in the masked raster.
In contrast, now I would like cells corresponding to a
"mask" NOT to display* in the main raster layer. Is there
a way to do it?
This is part of a larger issue I am addressing and that I
will briefly describe. In the attached sample image, you
see points imported via v.in.ascii and used to get the
green interpolated raster. Values at black points are
greater than zero, whereas the value of the white point is
zero (and it is not used for interpolation since it has no
biological meaning).
The end result would be to clip out a portion of the green
raster around the white point. This portion would be
delimited by midpoints between the white point and the
closest neighboring black points.
So far, I have been trying to get a vector buffer around
the white point and then v.to.rast for some kind of
subsequent clipping (described above*). However I have no
cue on how to get a comlex shape from neighboring points
as described. Is there a method already in place to do
this?
Many thanks in advance and any hints much appreciated,
Luigi
grass6/cygwin user
INFINITO ADSLFLAT 4 MEGA: SOLO 27,90 EURO AL MESE IVA INCLUSA IP STATICO, BANDA GARANTITA 256Kbps ANTIVIRUS E FIREWALL INCLUSI NEL PREZZO
