[GRASS-user] WMS fails on Geosciences Australia downloads

[Richard Chirgwin]

Hamish wrote:
> Richard:
>   
>> 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.
>   
Damn, I think you're right. The TIFF, which I thought included elevation 
data, seems to suffer a similar problem. Still, all is not lost, because 
I can get the elevation data from a vector map of the relevant area and 
create a real DEM ...

Richard
> if you look in the capabilities XML file you will see that geotiff is conspicuously missing from the available image formats:
>  http://www.ga.gov.au/wms/getmap?dataset=national&request=capabilities
>
>
> 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.
>
>
>
> Hamish
>
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