Hi, Many thanks for your response, Martin. So, it doesn't need to be a mistake. Just a flipped image.
The doubt raised because, for example, gdalbuildvrt doesn't accept ns positive resolution values. Looking at this old ticket http://trac.osgeo.org/gdal/ticket/3432, seems that that kind of raster data can't be mosaiced. You get an error. I don't understand why. I know cartesian coordinate system sets the origin in the bottom left corner, while images set the origin in the top left corner. So, the ns resolution of a georeferenced image is negative. Otherwise, you get a south up image. But... if all the images you want to mosaic have this "problem" (positive ns resolution), why I can't mosaic them using gdalbuiltvrt? Best regards, Jorge On Fri, Aug 10, 2012 at 6:09 PM, Martin Chapman <[email protected]> wrote: > Jorge, > > It's a south up image. If the gsd x value is negative the image is an > east to west image. Normally a north up image will have a positive gsd x > and a negative gsd y. > > Marty > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Jorge Arevalo > Sent: Friday, August 10, 2012 9:39 AM > To: [email protected] > Subject: [gdal-dev] What should I expect? > > Hello, > > If while I'm executing gdalinfo against a raster layer I get a positive > value for pixel size Y, what of these scenarios is possible? > > - The raster's map coordinate system sets the origin of the data in the > upper left corner. > - The raster is not georeferenced and its coordinates are interpreted as > image pixels, instead of map units. > - Any other situation (corrupt file?, other?) > > I know this value is almost always negative. For example, in case of UTM > coordinate system. But, how common is to have a positive value for Y > coordinate? > > Many thanks in advance > > -- > Jorge Arevalo > http://www.libregis.org > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Jorge Arevalo http://www.libregis.org _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
