[GRASS-dev] future thematic cartography in GRASS [was: Re: [GRASS GIS] #974: [Patch] add option to d.vect to make symbol size proportionate to square root of size_column]

[Hamish]

Moritz wrote:
> What is still missing right now is an easy way to display a
> combination of color-classified and proportionately sized
> symbols. It is possible to declare an arbitrary numeric
> column as z-height and use that with zcolor, but I don't
> think this is very straightforward and even though ISTR you
> don't see the need for that, cartographic theory (at least
> for thematic maps) still calls for reduced numbers of
> classes.

The debate rages on whether class-splitting is a good idea or not.
<2c> In my personal opinion it is open to huge misleading abuse both
intentional and unintentional, and so I try to avoid it. Probably
even more so than the potential to abuse statistics because it also
plays tricks on your visual perceptions. For raster maps the best
compromise I know is to include continuous color maps with contour
lines over the top. For vector maps I don't know of a good compromise,
or even if one is possible. </2c>

> However, if we go this way, I would need to add a flag to
> d.vect which allows sorting symbols with the largest in the
> back. This is absolutely necessary for readability. However,
> this implies a fundamental change in the d.vect code,

As this is just the beginning, I would prefer a new module for that
along the lines of d.vect.chart.

why not simplify the name to just "d.thematic"?


regards,
Hamish

ps- see also v.colors and the new extra/ring symbol