[Gvsig_english] Re: recommended raster exchange format

[Benjamin Ducke]

Tim Michelsen wrote:
> Benjamin Ducke schrieb:
>> The r.out.gdal module is not very good at guessing the right data type
>> for your data. You may need to experiment a bit with the "type" option.
>> If your data is floating point, try
>>
>> type=Float64
>>
>> In that case, of course, you will not be able store cell colours
>> directly in the TIFF file, meaning that you have to re-create
>> your palette in gvSIG.
> 
> I tried r.out.tiff and got a TIFF which I was able to load into gvSIG. 
> Unfortunately, the colortable option from the raster pilot was greyed 
> out on that layer. I guess because it had already a colortable attached 
> to it.

I think r.out.tiff is very limited in that it only exports 8-Bit
tiff images. In that case, gvSIG interprets the data as single band
and displays it as gray scale. There are no value ranges in the
image to use for categorization and thus no way for the Raster Pilot
to create a colour scheme.

What happens if you just add the layer using the "Georeference" tab
and tick the option to "use georeferencing"?

> I need to have a legend in my map printout with a colortable.

If all else fails, you can use d.out.png and geo-reference the
resulting raster manually (or copy a worldfile from a geo-referenced
raster of the same position and extent). Use d.legend to create a 
legend, export it with d.out.png and paste it as an image into the gvSIG
map layout. Not exactly elegant, but this way you should be able
to get your images and legends into a map layout.

> 
> All rasters I export from GRASS with r.out.gdal are not readable.
> A bad situation because all my analysis are well finished and now I 
> cannot get my data into gvSIG.

What do you mean by "not readable"? What do you see if you look at
the raster layer's properties? Is the spatial extent and resolution
OK? How about the data range?

> 
> But it seems that this is more a GRASS export problem since rasters 
> aren't also opening in QGIS.

It's actually a problem with there being no open standard raster
exchange format in the GIS world that can save georeferencing,
data and colour scheme information in one simple container and
would be supported by all GIS as reliably as, say shapefiles.
A clear case for the OGC, if you ask me.

Ben

> 
> Kind regards,
> Timmie
> 
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> 


-- 
Benjamin Ducke
Senior Applications Support and Development Officer

Oxford Archaeology Ltd
Janus House
Osney Mead
OX2 0ES
Oxford, U.K.

Tel: +44 (0)1865 263 800 (switchboard)
Tel: +44 (0)1865 980 758 (direct)
Fax :+44 (0)1865 793 496
benjamin.ducke at oxfordarch.co.uk




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