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?
First, you need to determine whether it's relief-shaded or if there's a direct relationship between the colour and the elevation. If it's the latter, the next step would be to convert it to a single-channel image, either grey-scale or indexed-colour using the correct palette ordering. That's the hard part. I suspect that you would be better off just grabbing the appropriate tile from the GTOPO30 dataset (given the name, there's a good chance that's where it came from in the first place). -- Glynn Clements <[EMAIL PROTECTED]> _______________________________________________ grassuser mailing list [email protected] http://grass.itc.it/mailman/listinfo/grassuser
