Selon Etienne Tourigny <[email protected]>: > 1) Probably a datum issue, as shapefiles do not include datum shift > information. You could work this around by making a new shape file > with the same datum as the gtiff file. > > What are the datums of your gtiff and shape files? Please post the > contents of the .prj file.
It might be the same as http://trac.osgeo.org/gdal/ticket/3947 > > Etienne > > On Mon, Jan 30, 2012 at 9:39 AM, Tilottama Ghosh <[email protected]> > wrote: > > Hi, > > > > I have a huge tiff image (covering an entire country) with 3399 columns and > > 3747 rows, so a total of 12,736,053 cells. The cell size is 1000m or 1km. I > > need to extract the data per km2. Of course, I didn't think it was smart to > > work with such a huge dataset in one go. So, I followd these steps in > > Quantum gis - > > > > 1. I used the gdalwarp -crop_to_cutline in the command line to carve out a > > portion of the raster image based on the shapefile of a state of the > entire > > country. The problem is that although the gdalwarp command worked it is > > clearly causing a shift (of about 500m) during this step. > > > > 2. Then, I used the gdal2xyz tool from the command line to create the csv > > file corresponding to the 'cut out' raster image or only the raster image > of > > the state. > > > > 3. Then I used the 'Create a Layer from a Delimited Text file' plugin in > > qgis to get the centroid shapefile. > > > > My problems are- > > > > 1. The shift in the image caused by the gdalward tool. Does anyone know how > > to work around that, so that no shift is caused? > > > > 2. The image is in 32 bit floating point and so does not show the attribute > > table. Even after getting the csv file I am unable to link the created csv > > file with the raster image, and thus cannot understand which pixel > > corresponds to which value in the csv file. > > > > Can anyone suggest any better way of doing this? > > > > Thanks very much for your help. > > > > Best Regards, > > > > Tilo > > > > > > -- > > > > _______________________________________________ > > Qgis-user mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/qgis-user > > > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user > _______________________________________________ Qgis-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-user
