[GRASS-user] Re: BAnk and ditch symbols in grass (or other Open Source GIS)

[Hamish]

> Michael wrote:
> > I wonder if an enterprising programmer could start with the
> > d.rast.arrow code and use it to allow different symbols than
> > arrows?
> 
> FYI I am already well underway on that, have half-written a new
> module called d.barb. Primarily for drawing wind barbs on met
> maps, but also allows things like straws instead of arrows.
> 
> input is either from a raster map array like d.rast.arrow, or
> a vector map with direction and magnitude taken from the points'
> attribute table.

(I should mention that I've been "well underway" on that for more than
a year, it's been stalled while I waited for a job to come up that needed
it so I could justify my time. I hesitated to put it into addons svn
as it is still pre-alpha, but if anyone wants to collaborate on it I'm
happy to put it up there)


as for the hatched lines for banks and depressions, continuing on with the
idea of using 'v.split length=' in a loop with length taken from each line
segment's attribute table to set the density, then 'v.to.points -v' to pull
out the vertices, then something to upload the tangent slope of the line
at each vertex to that point's attribute table, then using 'd.vect size_column= rotate_column=' to render a symbol (centered at 0,0) at 90+20
degrees to the line, of the appropriate length (negative length could be
right side of line instead of left, copy idea for that from v.lrs.segment?).

and so for different line segments you get different hatching styles.

not really automatic, but enough for a prototype or one-off proof of
concept before getting into it with a full module.

?
Hamish