[GRASS-user] trying to get unprojected raster data into a projected location

[Pietro Calogero]

Thank you. GDAL has capabilities I was not aware of. Part of the  
challenge here is that some ArcView users do not generate .proj files  
even with shapefiles (not automatic in 3.2), and generally the GIS  
users around here operate in metric units, so using the Lat-Lon  
location cannot work. And I have not figured out how to change an x,y  
location so that data can be reprojected from it into UTM.
In a case where I do not have a match as described earlier, I guess I  
will need to use the georeference tool to generate proj data before  
importing. I have done that easily in QGis with 6 MB Google Earth  
mashup TIFs, so I suppose the method is similar for unreferenced  
shapefiles. But I'm not sure how QGIS handles a 5GB .sid file.
Pietro Calogero
http://www.calogero.us/Kabul/2007/

On Sep 23, 2007, at 8:37 AM, Hamish wrote:

> 5. The imported vectors and raster line up, so at least I have
> replicated the registration of the original ArcGIS coverage.

'r.in.gdal -o' doesn't pay any attention to the g.region settings, it  
just uses
the data in the file.

If it imported as south and west = 0, and north and east = number of  
pixels,
with a resolution of 1, r.region can be used to reset that if the  
correct
values are known. (that won't work in lat/lon location where the  
number of
vertical pixels exceeds 90 (ie can't be north of the north pole),  
then the
import fails [devs: in that case should we rescale the import in  
r.in.gdal to
y=0-1?])

> So in this procedure I only created the x,y location to extract
> information from the .sid file: its extents and resolution. I never
> pulled data into the x,y location. Thank God, because that raster
> takes 2 hours to import into any location!

gdalinfo should be able to give you that info without importing it.
gdal_translate might let you assign georeferencing info to the image  
if you
wanted to do that, but as a new file.


Hamish




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