Hello,
It would be useful to be able to use something similar to r.mask to be able to limit the area that v.voronoi (or other programs) use. Is there a way to mask out particular areas?
Bill B.
Hello,
currently there is no MASK support for vector data. Only solution is
to extract a subset of whole dataset into new vector map/layer with
existing GRASS tools (i.e. v.extract and others).
Also MASK concept for vector data is easy to implement for vector
points but it gets tricky with lines/areas. What should happen to
line/area that crosses MASK border?
Also as MASK normally is applied "on fly", it could be real show
stopper when working with large datasets (i.e. LiDAR data).
WBR,
Maris.
2008/10/1 William L. Baker <bakerwl@uwyo.edu>:
Hello,
It would be useful to be able to use something similar to r.mask to be able
to limit the area that v.voronoi (or other programs) use. Is there a way to
mask out particular areas?Bill B.
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grass-user@lists.osgeo.org
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Another thing (which I'd like to see in GRASS 7.0) would be to have a
where parameter for all v. modules which would allow one to filter the
points based on the attributes (usually this is enough)
--Wolf
On 01.10.2008 21:03, Maris Nartiss wrote:
Hello,
currently there is no MASK support for vector data. Only solution is
to extract a subset of whole dataset into new vector map/layer with
existing GRASS tools (i.e. v.extract and others).Also MASK concept for vector data is easy to implement for vector
points but it gets tricky with lines/areas. What should happen to
line/area that crosses MASK border?
Also as MASK normally is applied "on fly", it could be real show
stopper when working with large datasets (i.e. LiDAR data).WBR,
Maris.2008/10/1 William L. Baker <bakerwl@uwyo.edu>:
Hello,
It would be useful to be able to use something similar to r.mask to be able
to limit the area that v.voronoi (or other programs) use. Is there a way to
mask out particular areas?Bill B.
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
--
<:3 )---- Wolf Bergenheim ----( 8:>
Yes, that would be useful too.
Yes, in the case of vector points, a MASK-like function would be conceptually simpler than dealing with vector lines and polygons.
v.voronoi produces lots of spurious polygons if there is lots of space without points outside where the points actually lie, which occurs if a study area has an irregular shape (not rectangular). Thus, some kind of buffer around the points is needed to set limits on the analysis space. I think someone is revising this program, and perhaps this problem can be addressed, but it may not be easy to program. A more general MASK solution would be useful for all point-based programs.
Bill B.
Wolf Bergenheim wrote:
Another thing (which I'd like to see in GRASS 7.0) would be to have a
where parameter for all v. modules which would allow one to filter the
points based on the attributes (usually this is enough)--Wolf
On 01.10.2008 21:03, Maris Nartiss wrote:
Hello,
currently there is no MASK support for vector data. Only solution is
to extract a subset of whole dataset into new vector map/layer with
existing GRASS tools (i.e. v.extract and others).Also MASK concept for vector data is easy to implement for vector
points but it gets tricky with lines/areas. What should happen to
line/area that crosses MASK border?
Also as MASK normally is applied "on fly", it could be real show
stopper when working with large datasets (i.e. LiDAR data).WBR,
Maris.2008/10/1 William L. Baker <bakerwl@uwyo.edu>:
Hello,
It would be useful to be able to use something similar to r.mask to be able
to limit the area that v.voronoi (or other programs) use. Is there a way to
mask out particular areas?Bill B.
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
William L. Baker wrote:
v.voronoi produces lots of spurious polygons if there is lots of space
without points outside where the points actually lie, which occurs if a
study area has an irregular shape (not rectangular). Thus, some kind of
buffer around the points is needed to set limits on the analysis space.
If v.hull is no-good for areas shaped like a "C", perhaps v.buffer +
"v.clean -> remove small areas" or v.buffer then v.centroids+v.dissolve
would do a better job?
and don't forget v.select which is much faster than v.overlay.
Hamish
On 02.10.2008 04:06, William L. Baker wrote:
I think someone is revising this program, and perhaps this problem can
be addressed, but it may not be easy to program.
Yes Martin Pavlovsky is working v.voronoi2, as part of the Google Summer
of Code program, and he told me there should be a working first version
of it ready in about two weeks (in addons).
Martin, does your v.voronoi2 suffer from these kinds of problems? What
would you say to adding a where parameter that would allow one to limit
the points with an SQL query?
--Wolf
Bill B.
Wolf Bergenheim wrote:
Another thing (which I'd like to see in GRASS 7.0) would be to have a
where parameter for all v. modules which would allow one to filter the
points based on the attributes (usually this is enough)--Wolf
On 01.10.2008 21:03, Maris Nartiss wrote:
Hello,
currently there is no MASK support for vector data. Only solution is
to extract a subset of whole dataset into new vector map/layer with
existing GRASS tools (i.e. v.extract and others).Also MASK concept for vector data is easy to implement for vector
points but it gets tricky with lines/areas. What should happen to
line/area that crosses MASK border?
Also as MASK normally is applied "on fly", it could be real show
stopper when working with large datasets (i.e. LiDAR data).WBR,
Maris.2008/10/1 William L. Baker <bakerwl@uwyo.edu>:
Hello,
It would be useful to be able to use something similar to r.mask to
be able
to limit the area that v.voronoi (or other programs) use. Is there a
way to
mask out particular areas?Bill B.
_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
--
<:3 )---- Wolf Bergenheim ----( 8:>