None of those resampling methods are well-suited to classified rasters as far as I can tell.
The method that has worked best in the past was to take the majority of a number of the nearest neighbors. The 'mode' algorithm in gdaladdo may do that, but I haven't checked the source code. Jack. -- mathuin at gmail dot com 2012/1/27 Dmitry Baryshnikov <poli...@mail.ru>: > 27.01.2012 23:30, John Twilley пишет: > >> Cubic is fine for the elevation, but it doesn't work on the landcover. >> which is the problem I originally mentioned. >> >> Jack. >> -- >> mathuin at gmail dot com >> >> >> >> 2012/1/27 Dmitry Baryshnikov<poli...@mail.ru>: >>> >>> 27.01.2012 20:19, John Twilley пишет: >>> >>>> After retrieving the files and building VRTs from them, I run the >>>> following gdalwarp commands: >>>> >>>> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5 >>>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 -te >>>> 2002944 2271744 2016768 2288640 \ >>>> -srcnodata -340282346638528859811704183484516925440 -dstnodata 0 >>>> ND302HT.vrt ND302HT.tif >>>> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5 >>>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 -te >>>> 2002944 2271744 2016768 2288640 \ >>>> -srcnodata 255 -dstnodata 11 L0102HT.vrt L0102HT.tif >>>> >>>> The only differences between the lines are the nodata values. >>>> >>>> Jack. >>>> -- >>>> mathuin at gmail dot com >>>> >>>> >>>> >>>> On Thu, Jan 26, 2012 at 22:49, Dmitry Baryshnikov<poli...@mail.ru> >>>> wrote: >>>>> >>>>> 27.01.2012 3:39, John Twilley пишет: >>>>>> >>>>>> I am working with elevation and landcover data downloaded from the >>>>>> USGS. I use gdalwarp to convert the data to a much smaller pixel. The >>>>>> elevation data works very nicely with cubic resampling, but the only >>>>>> resampling that works at all for the landcover data is >>>>>> nearest-neighbor and that's very blocky. When I last worked with >>>>>> landcover data, I used a majority algorithm which produced smoother >>>>>> output -- but that algorithm is not implemented in gdalwarp. >>>>>> I am looking over the source to gdalwarp to see how hard it is to add >>>>>> a new algorithm. Other than that, though, what options are available >>>>>> to me? Thanks in advance! >>>>>> Jack.-- >>>>>> mathuin at gmail dot com >>>>>> _______________________________________________ >>>>>> gdal-dev mailing list >>>>>> gdal-dev@lists.osgeo.org >>>>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >>>>>> >>>>>> >>>>> Hi John, >>>>> >>>>> That is your command line string for gdalwarp? >>>>> >>>>> Best regards, >>>>> Dmitry >>>>> >>>>> _______________________________________________ >>>>> gdal-dev mailing list >>>>> gdal-dev@lists.osgeo.org >>>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >>> >>> Hi John, >>> >>> Try to add "-r cubic" command parameter >>> For example: >>> >>> >>> gdalwarp -q -multi -t_srs "+proj=aea +datum=NAD83 +lat_1=29.5 >>> +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0 +y_0=0 +units=m" -tr 6 6 -r cubic >>> -te >>> >>> 2002944 2271744 2016768 2288640 \ >>> -srcnodata -340282346638528859811704183484516925440 -dstnodata 0 >>> ND302HT.vrt ND302HT.tif >>> >>> You can found additional parameters description here: >>> http://www.gdal.org/gdalwarp.html >>> I have tested -r parameter and it works. >>> >>> >>> Best regards, >>> Dmitry >>> >>> >>> _______________________________________________ >>> gdal-dev mailing list >>> gdal-dev@lists.osgeo.org >>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >> >> > Hi John, > You can use resampling methods: > near: nearest neighbour resampling (default, fastest algorithm, worst > interpolation quality). > bilinear: bilinear resampling. > cubic: cubic resampling. > cubicspline: cubic spline resampling. > lanczos: Lanczos windowed sinc resampling. > > And what method do you need? > > > Best regards, > Dmitry > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
