I'm trying to determine the default method of rasterization used by v.to
rast.
In the v.to.rast manual it states in relation to the -d option, that 'All
cells touched by the line will be set, not only those on the render path',
but I'm not certain which method is being used by default.
I came across a paper by Biagi and Negretti
<http://geomatica.como.polimi.it/workbooks/n2/articoli/lbmn.pdf> * which
describes how by default vectors are rasterized in GRASS 5. The latter
authors refer to the 'center' method as being the standard GRASS command in
5.0 (p. 4). Is this used in GRASS 7? From my observation (in the Map
Display), by default, vector area appear to be rasterized if the center of
the grid cell falls within the area boundary?
I haven't checked through the code, but maybe someone has some knowledge on
the history of v.to.rast?
I'm trying to determine the default method of rasterization used by v.to
rast.
In the v.to.rast manual it states in relation to the -d option, that 'All
cells touched by the line will be set, not only those on the render path',
but I'm not certain which method is being used by default.
I came across a paper by Biagi and Negretti
<http://geomatica.como.polimi.it/workbooks/n2/articoli/lbmn.pdf> * which
describes how by default vectors are rasterized in GRASS 5. The latter
authors refer to the 'center' method as being the standard GRASS command in
5.0 (p. 4). Is this used in GRASS 7? From my observation (in the Map
Display), by default, vector area appear to be rasterized if the center of
the grid cell falls within the area boundary?
Binary file OBJ.x86_64-unknown-linux-gnu/vect2rast.o matches
Binary file OBJ.x86_64-unknown-linux-gnu/do_lines.o matches
Binary file OBJ.x86_64-unknown-linux-gnu/do_areas.o matches
Binary file OBJ.x86_64-unknown-linux-gnu/support.o matches
do_areas.c:42: if (ISNULL(&cat)) { /* No centroid or no category */
do_areas.c:94: int i, centroid, nareas_selected;
do_areas.c:114: centroid = Vect_get_area_centroid(Map, i + 1);
do_areas.c:116: if (centroid <= 0) {
do_areas.c:117: G_debug(2,_("Area without centroid (OK for island)"));
do_areas.c:120: Vect_read_line(Map, NULL, Cats, centroid);
do_areas.c:127: G_debug(2, _("Area centroid without category"));
do_areas.c:131: /* field < 1, process all areas with centroid */
v.to.rast.html:41:Labeled areas and/or centroids will produce filled raster coverages with edges
v.to.rast.html:49:Points and orphaned centroids will be converted into single cells on the
vect2rast.c:219: /* maximum possible numer of areas: number of centroids
vect2rast.c:221: * number of areas with centroid that are within cat constraint
Nikos
but maybe someone has some knowledge on
the history of v.to.rast?
On Mon, Feb 23, 2015 at 1:05 PM, RichardCooper <richtcooper@hotmail.com> wrote:
Hi,
I'm trying to determine the default method of rasterization used by v.to
rast.
In the v.to.rast manual it states in relation to the -d option, that 'All
cells touched by the line will be set, not only those on the render path',
but I'm not certain which method is being used by default.
The -d option applies only to lines, default is only those on the
render path (thin line).
I came across a paper by Biagi and Negretti
<http://geomatica.como.polimi.it/workbooks/n2/articoli/lbmn.pdf> * which
describes how by default vectors are rasterized in GRASS 5. The latter
authors refer to the 'center' method as being the standard GRASS command in
5.0 (p. 4). Is this used in GRASS 7? From my observation (in the Map
Display), by default, vector area appear to be rasterized if the center of
the grid cell falls within the area boundary?
Yes, or the other way around: a grid cell belongs to the area where
the grid cell's center falls into.
Markus M
I haven't checked through the code, but maybe someone has some knowledge on
the history of v.to.rast?
On Tue, Feb 24, 2015 at 9:19 AM, Markus Metz
<markus.metz.giswork@gmail.com> wrote:
On Mon, Feb 23, 2015 at 1:05 PM, RichardCooper <richtcooper@hotmail.com> wrote:
Hi,
I'm trying to determine the default method of rasterization used by v.to
rast.
In the v.to.rast manual it states in relation to the -d option, that 'All
cells touched by the line will be set, not only those on the render path',
but I'm not certain which method is being used by default.
The -d option applies only to lines, default is only those on the
render path (thin line).
I came across a paper by Biagi and Negretti
<http://geomatica.como.polimi.it/workbooks/n2/articoli/lbmn.pdf> * which
describes how by default vectors are rasterized in GRASS 5. The latter
authors refer to the 'center' method as being the standard GRASS command in
5.0 (p. 4). Is this used in GRASS 7? From my observation (in the Map
Display), by default, vector area appear to be rasterized if the center of
the grid cell falls within the area boundary?
Yes, or the other way around: a grid cell belongs to the area where
the grid cell's center falls into.
I've made an attempt to add that to the manual (r64752 and r64753).