[GRASS-user] exporting maps via gdal

[Jachym Cepicky]

thanks for hints

we will see

jachym

On Mon, Jul 17, 2006 at 10:41:17AM -0700, Matthew Perry wrote:
> Jachym,
> 
> On 7/17/06, Jachym Cepicky <jachym.cepicky at centrum.cz> wrote:
> >> > trying to export some floating point map (result of interpolation) to
> >> > geotiff via gdal:
> >> >
> >> >     r.out.gdal in=ca2005 out=ca2005.tif type=Float32
> >> >
> >> > result is, that the map is displayed as "black" e.g. in qgis and
> >> > mapserver is not able to display anything :-(
> >> >
> >> Jachym,
> >>
> >> you could try to export to ERDAS/IMG format (format=HFA).
> >> Maybe then the color tables is preserved.
> >>
> >> Markus
> >
> >hmm, problem is, that the map can not be displayed via mapserver - how
> >do you export any floting point geotiff ?
> >
> >thanks
> >    jachym
> >
> 
> The r.out.gdal output *can* be displayed with mapserver but, since it
> has no associated color palette (that mapserver can understand
> anyhow), mapserver will render it in a black->white color ramp. If
> your data values are very skewed, it may appear all black. Try using
> the SCALE processing directive to set the min and max of the b&w color
> ramp. 
> (http://mapserver.gis.umn.edu/docs/howto/raster_data/#special-processing-directives)
> 
> Also, Have you tried r.out.tiff ? This will export a colored image of
> your data at the current region settings. The resulting tiff will not
> contain actual values but will look as it did in grass.
> 
> r.out.tiff -t input=elevation.dem output=elev
> 
> You can use the r.out.tiff output for display purposes and the
> r.out.gdal output for query purposes.
> 
> Finally you might want to try reading the grass raster directly from
> mapserver and avoid the conversion step altogether.
> 
> 
> -- 
> Matt Perry
> perrygeo at gmail.com
> http://www.perrygeo.net

-- 
Jachym Cepicky
e-mail: jachym.cepicky at centrum.cz
URL: http://les-ejk.cz
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