[GRASS-user] Display arrows on basis of vector points

Hamish hamish_nospam at yahoo.com
Tue May 23 20:43:04 EDT 2006


> > > Does anybody know if it's possible to display arrows starting from
> > > vector points which have a x_shift and y_shift attribute for their
> > > direction/length.
> > >
> > > I would like to use it for displaying flow velocities of glaciers!
..
> > I am not sure if this is currently possible outside of a custom
> > script involving d.mapgraph -- but it is quite simple to do in R
> > with the arrow() function.

FYI, d.mapgraph is depreciated in GRASS 6.1, use the much improved
"d.graph -m" instead. Maybe modify the arrow symbol (or make 8, 1 for
each dirn), with tail at 0,0. See display symbol help in the wiki
add-ons. Support for custom rotation is still not finished for symbols.

> Do you know about d.rast.arrow? It takes a grid of directions and a
> optional grid of magnitudes and can generate vector fields. I use it
> to plot wave and current fields.

(again, GRASS 6.1-cvs version only)
screenshots:
 http://bambi.otago.ac.nz/hamish/grass/d_rast_arrow_360.png
 http://bambi.otago.ac.nz/hamish/grass/d_rast_arrow_360b.png
 http://bambi.otago.ac.nz/hamish/grass/d_rast_arrow_magnitude.png


Hamish




More information about the grass-user mailing list