On 21/03/08 15:51, Jarek Jasiewicz wrote:
Moritz Lennert wrote:
On 20/03/08 17:15, Jarek Jasiewicz wrote:
Moritz Lennert wrote:
On 20/03/08 11:17, Jarosław Jasiewicz wrote:
Hi I have lots of raster, thinned lines and second raster with with
one line. I must find all points where second line intersect with
lines on first raster
it is very simple:
r.mapcalc points=if(raster_two==1&&raster_one==1,1,null())
but there is one exception:
AB
BA
when lines intersect with 45 grades. There is intersection but
without common point. Naither buffor nor grow is not a solution
because I need exactly one point lying exactly on line from raster one
Any Ideas
Either ressample your rasters to coarser resolution to make them
coincide, or convert to vector and use a combination of v.patch +
v.clean (e.g. v.clean input=lines1 output=lines2 err=points tool=break)
Moritz
thanks for ansfer
I tried it with similar way (v.patch +v.clean + topology report) but
it is not it. I need EXACT coordinates of pixels on intersection do
to transfer it to another program
The map points (created with the parameter err=points) should contain
exactly these points. Obviously this only works if you can create
correct vector lines from your raster.
See example here:
http://geog-pc40.ulb.ac.be/grass/misc/intersections.html
Moritz
yes, but real (single prescision) coordinates of the point are not exact
of coordinates of pixel,
for example:
point: x=3567891.36345671, y=x=6564456.8176236
pixel: x=3567891.36357892, y=x=6564456.8339658
but, v.to.rast and r.to.vect solve that problem
It would be interesting to know where the difference comes from...
AFAIK, coordinates are always coded at the same precision, both for
raster and vector, but I might be wrong.
Just out of curiosity: what types of units are you working in for such a
precision to make sense ?
Moritz
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