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

Hamish hamish_nospam at yahoo.com
Mon Aug 27 05:04:46 EDT 2007

WolfgangZ wrote:
> 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?

As this is a WMS server, maybe r.in.wms's "list layers" option shows some
elevation options? Worth a look..

Otherwise, it's possible, but you'd have to do a fair bit of work which
may not be worth the effort.

> PS: I'm sorry for being a bit off topic, as this is not mainly grass 
> related.

IHO interesting problems are not OT if grass can be the tool to solve


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