[!! SPAM] [GRASS-user] OT: converting color graphic to height data possible?

Vincent BAIN bain at toraval.fr
Sun Aug 26 09:47:37 EDT 2007

Hello Wolfgang,
I fear the image you point is lightly shaded, so the color table won't 
fit the elevation model (hope I'm wrong...)


WolfgangZ a écrit :
> Hi,
> I found a layer on a web map server that shows elevation data (no 
> shaded relief as I think). Is it possible to convert the color 
> information that is in the image back to elevations? Here a link to 
> one image:
> http://mapas.topografia.upm.es/cgi-bin/gtopo?SERVICE=WMS&VERSION=1.1.1&REQUEST=GETMAP&LAYERS=spain25mtintashipsometricas&SRS=EPSG:23030&BBOX=535900,4779200,545900,4789200&WIDTH=200&HEIGHT=200&FORMAT=image/tiff 
> I suppose r.mapcalc would be the tool to use, but it seems not 
> possible without the right color map. Any suggestions?
> Kind regards
> Wolfgang
> PS: I'm sorry for being a bit off topic, as this is not mainly grass 
> related.
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