[GRASS5] [bug #3704] (grass) d.rast.arrow does not save a line in the monitor history

[Harmish Bowman via RT]

Ok, d.rast.arrow and d.rast.num are now added to the display monitor history
list and should survive redraw, PNG export, zoom, etc.


Also for d.rast.arrow I've added support for compass based aspect maps
(degrees clockwise from north) and 360 degree resolution instead of D8 (where
applicable).

i.e.
 grass aspect maps:    1 deg resolution
 compass aspect maps:  1 deg resolution
 AGNPS aspect maps:    D8 resolution (45 degrees)
 ANSWERS aspect maps:  15 degree resolution


Two things to think about:
- How to visualize MDF directional flow created by r.terraflow?

- With a little more effort, arrow size (magnitude) could be read
  from a second raster map, perhaps with a default scaling factor which
  could take the max of the raster range to be 10x the cell width.
  i.e. Eulerian velocity fields!


screenshot:
  http://bambi.otago.ac.nz/hamish/grass/d_rast_arrow_360.png



enjoy,
Hamish


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