[GRASS-user] azimuth of lines with v.to.db?

[Maciej Sieczka]

Carlos "Guâno" Grohmann wrote:
> This is almost what I need. I need the results to be in range 0-360,
> from North. So I can get a rose diagram, with petals weighted
> according to azimuth frequency or to azimuth lenght, like the
> attachment.

I've just remember PROJ.4's geod [1]. Example:

$ echo "50N 19E 51N 20E" | geod -I +ellps=WGS84 +units=m
32d8'43.417"    -147d4'58.6"    131935.963

The 1st 2 numbers are azimuth from the 1st to 2nd point and
back, respectively, 3rd is the distance between them.

[1]http://proj.maptools.org/man_geod.html

Maciek