[GRASS-user] WMS fails on Geosciences Australia downloads

Hamish hamish_b at yahoo.com
Wed May 14 05:40:35 EDT 2008

> I hope this is the last maddening issue; working with:
> g.region n=33S s=34S w=150 e=151 nsres=00:00:05 ewres=00:00:05
> r.in.wms -c
>  mapserv="http://www.ga.gov.au/wms/getmap?dataset=national&"
>  -g layers=dem_9sec output=dem_9sec format=png srs=EPSG:3112
> (The small region keeps the the tile size down)
> I get the 9-second DEM. It looks and displays okay, but the
> elevation data is wild.
> r.what -f input=dem_9sec at PERMANENT
> east_north=150.8177882,-33.785157971
> produces:
> 150.8177882|-33.785157971||31407|
> Since I can reasonably assume that the elevation isn't
> 31,407 metres, nor that the elevation in the mountains
> is lower than near the ocean, something's awry with the
> elevation...

I am afraid you are not looking at the elevation, but rather the color palette entry of the PNG file. ie this is a "visual only" exercise.
WMS servers can dish up real data, but I suspect that to do that they need to support geotiff format, and the GA server only provides tiff/png/jpeg/wbmp pretty imagery. I'm not sure about that though, maybe someone reading knows better about this.

if you look in the capabilities XML file you will see that geotiff is conspicuously missing from the available image formats:

If you find no joy, I'd suggest contacting Geosci Aust and asking about it; and also on the Aust-NZ OSGeo mailing list as well. There are some talented people at both places who may be able and keen to help.



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