[GRASS-dev] Scale display in GRASS Monitor

[Glynn Clements]

Antonello Andrea wrote:

> > Given all these problems, I wonder how
> > - qgis
> > - udig
> > - ESRI
> > - Mapserver
> > - ...
> > 
> > are displaying the scale? All fooling the user? GRASS is probably the
> > only GIS in the world not displaying a scale (how does d.barscale work?).
> 
> I didn't follow the whole discussion, so I hope I'm answering to what
> was asked...
> 
> I can only tell about JGrass. We have a scalebar and yes, if you want to
> see it like that, somehow we are fooling the user, even if of a very small 
> amount (I never needed it precise on the monitor). Since we retrieve the 
> resolution from the drivers, We are exposed to the problems listed above.
> 
> But I don't really mind about measuring the screen with a ruler, the important 
> to me is to get the proper result when I print the map.
> And on paper the scale I see on the screen is returned to me with a millimetric
> precision which that is what I need.

For printing, determine the scale factor is straightforward, as
PostScript works in physical units. Of course, that fails if someone
rescales the PostScript file afterwards, or makes a photocopy at 70%,
etc.

It's a lot more robust to just use a scale bar like d.barscale.

-- 
Glynn Clements <glynn at gclements.plus.com>