[GRASS-user] OT: converting color graphic to height data possible?
glynn at gclements.plus.com
Sun Aug 26 22:04:38 EDT 2007
> 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:
> 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 <glynn at gclements.plus.com>
More information about the grass-user