[GRASS-dev] Re: [GRASS-user] How to find out an angle between to points on the map (for r.plane, r.lake)

[Dylan Beaudette]

On Thu, Feb 28, 2008 at 7:26 PM, Hamish <hamish_b at yahoo.com> wrote:
> Dylan Beaudette wrote:
>  > > Well of course I had to go and try this out.
>  > >
>  > > attached is a patch (against todays SVN) to optionally print the
>  > > bearing between clicks.
>
>
>  Hi,
>
>  you should add a check so that it won't allow bogus results if the
>  location is in Lat/Lon:
>
>  e.g. from d.grid:
>  if (geogrid->answer && G_projection() == PROJECTION_LL)
>   G_fatal_error(_(".. option is not available for LL projection"));
>
>  (the great circle line's bearing changes with distance along it; unless
>  you are interested in the rhumbline?)
>
>
>  for this stuff also checkout m.cogo, r.transect, r.profile,
>  d.rhumbline, d.geodesic
>
>
>  Hamish
>

Thanks for the tips. Before I go and make any more modifications /
documentation additions does this small patch appear to be useful
enough to be merged into d.measure ? The m.cogo module is useful
enough, but sometimes an interactive quick approach (such as what
d.measure does) can be extremely useful.


Dylan