[GRASS-user] Coordinates from distances

GRASS GRASS user
1

Hi all,

Might be a bit off topic but here we go:
I need to calculate coordinates for several points, something similar
to m.cogo, but instead of having distance + bearing information, I'll
have distance from at least 3 fixed, known landmarks. Is there a tool
already built for this? If not, I tough about using a combination of
v.buffer + v.overlay in order to cross circles representing the
possible location of each point from the landmarks.

Thanks
Daniel

2

Daniel wrote:

Might be a bit off topic but here we go:
I need to calculate coordinates for several
points, something similar to m.cogo, but instead
of having distance + bearing information, I'll
have distance from at least 3 fixed, known
landmarks. Is there a tool already built for
this?

not that I know of, but see also v.in.geodesic and
v.transect(s) in addons and the r.transect module.

If not, I tough about using a combination of
v.buffer + v.overlay in order to cross circles
representing the possible location of each point
from the landmarks.

yup, my first try would be v.buffer + v.patch +
'v.clean tool=break error=intersection_points', but
the Venn overlap area made by v.overlap may be
better if the ranges are sloppy.

http://grass.osgeo.org/grass60/screenshots/images/fire2.png

see also this previous investigation into using
distance from cell phone towers to find lost hikers:

http://grass.osgeo.org/wiki/Search_and_Rescue#Case_Studies

Hamish

3

Hi Hamish,

Thanks for the help. The search and rescue exemples are realy
interesting. Just one question though. I can find v.overlay in the
grass manual but I cannot find v.overlap (for the Venn overlap
area)... is that an add on? Did not find it in the addon repository
also...

Thanks
Daniel

On Sun, Feb 5, 2012 at 6:51 PM, Hamish <hamish_b@yahoo.com> wrote:

Daniel wrote:

Might be a bit off topic but here we go:
I need to calculate coordinates for several
points, something similar to m.cogo, but instead
of having distance + bearing information, I'll
have distance from at least 3 fixed, known
landmarks. Is there a tool already built for
this?

not that I know of, but see also v.in.geodesic and
v.transect(s) in addons and the r.transect module.

If not, I tough about using a combination of
v.buffer + v.overlay in order to cross circles
representing the possible location of each point
from the landmarks.

yup, my first try would be v.buffer + v.patch +
'v.clean tool=break error=intersection_points', but
the Venn overlap area made by v.overlap may be
better if the ranges are sloppy.

http://grass.osgeo.org/grass60/screenshots/images/fire2.png

see also this previous investigation into using
distance from cell phone towers to find lost hikers:

http://grass.osgeo.org/wiki/Search_and_Rescue#Case_Studies

Hamish

4

Daniel wrote:

Thanks for the help. The search and rescue exemples are
realy interesting. Just one question though. I can find
v.overlay in the grass manual but I cannot find v.overlap
(for the Venn overlap area)... is that an add on?
Did not find it in the addon repository also...

just a wordo on my part, I meant to write v.overlay.

for commands used to make that Venn diagram see the bottom of
the vector screenshots page on the website.

Hamish