[GRASSLIST:3233] Re: Missing 'output' in d.his (& d.shadedmap)

[Markus Neteler]

Karine,

On Tue, Feb 26, 2002 at 04:28:51PM +0100, Karine ZUERCHER wrote:
> Glynn,
> 
> Thanks a lot for your enlightenment!
> 
> I use the shaded maps only to produce backround images (of let's say a 
> geology raster layer shaded with a topography-aspect, so you get an idea of 
> geology and relief in the flat 2d map view), images I then want to use as 
> base layer in a GIS-web application.
> (More an esthetics use maybe. But I like the speed of d.rast to get the PNG 
> image... . 
> And maybe I'm doing those maps the wrong way...
> I was always wondering, if using an Aspect map was the right way to show 
> relief.)

concerning the latter: You may want to try

 shade.rel.sh altitude=30 azimuth=270 elevation=elevation.dem

and use the resulting shade map for shading. In my opinion the
result is nicer than using the aspect map from r.slope.aspect (due to
the different sun angle). Of course you may play with the
settings.
There are some funny differences with visual perception:
Some people see the relief inverted on a shaded DEM with certain
sun angles. You may try with your collegues (try the opposite sun
position and ask two or three collegues, 2-3 are usually enough to 
get different answers where valleys and ridges are located...).
 
Best regards

 Markus Neteler

> 
> On Tuesday 26 February 2002 15:39, Glynn Clements wrote:
> > What I meant is that I don't know of any situation where a colour
> > image *has* to be represented as a single composite colour layer. For,
> > anything that can be done with a composite layer, there should be an
> > equivalent process which works with separate R/G/B layers, except that
> > using separate layers will result in higher quality.
> >
> > E.g.
> >
> > display		d.rast		->	d.rgb
> > print		ps.map "raster"	->	ps.map "rgb"
> > export		r.out.ppm	->	r.out.ppm3
> > import		r.in.ppm	->	r.in.ppm -b
> >
> > > Thanks for the typ, although it's a longer way, it works fine.
> > >
> > > Still, if possible, I would suggest the reput the d.his  (& d.shadedmap)
> > > output option !
> >
> > The old behaviour was largely a result of the fact that d.his used to
> > generate a composite colour version of the data for output; the
> > "output=" option just saved data which was already being generated.
> >
> > d.his was changed to use the RGB raster functions (R_RGB_raster()
> > etc), as this produces better output. So, it no longer generates the
> > data which was being saved by the "output=" option.
> 
> In Kindness
> Karine
> -- 
> Karine ZUERCHER
> 
> kzuerch at yahoo.com

-- 
Markus Neteler

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