On Mon, Oct 28, 2013 at 8:55 AM, Ivan Marchesini <[email protected]> wrote: > Dear all, > I'm using gdalwarp to reproject a wgs84 srtm (3 arcseconds) tile to a > projected utm zone. I do not set "-tr" or "-ts" options, hence the final > output resolution is estimated by the gdalwarp module itself. > > For my tile I obtained an output resolution of 81.19 meters and I'm > wondering if one could explain which is the rationale behind this value. > > Many thanks > > Ivan > > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev
Forgot the list... Ivan, gdalwarp uses GDALSuggestedWarpOutput: http://gdal.org/gdal__alg_8h.html#a816819e7495bfce06dbd110f7c57af65 The docs state: """ ... Then a resolution is computed with the intent that the length of the distance from the top left corner of the output imagery to the bottom right corner would represent the same number of pixels as in the source image. Note that if the image is somewhat rotated the diagonal taken isn't of the whole output bounding rectangle, but instead of the locations where the top/left and bottom/right corners transform. The output pixel size is always square. This is intended to approximately preserve the resolution of the input data in the output file. ... """ Essentially it tries to match the size of the source image in x size and y size. kss -- Kyle _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
