Thank you Holger! That are great and very interesting advices! Bye, Benjamin
Am 23. März 2011 20:51 schrieb Holger Schöner <[email protected]>: > Hi Benjamin, > > Am Mittwoch, 23. März 2011, um 15:14:58 schrieb Sisyphos: >> @Holger: Are there for each >> zoomlevel individual raster layers/files used? > > No, I prepare a raster for the most detailed zoom level, and include that as > one layer in the mapnik style. This might not be optimal concerning rendering > speed, but so far that was not a problem for me. > >> 1. My files are not as nice as Hogleres files are. What would you >> suggest to smooth them. Is it possible to smoth them using gdal? Or is > > The mentioned renderings are based on CIAT/CGIAR hole-filled SRTM data (as > that > data has an incompatible license wrt. CC BY SA, the page was meant to not be > public, and I sent the email to you in private intentionally; unfortunately I > forgot to mention, that it should not be made public ...). > > The quality would usually not be sufficient to the highest zoom levels I use. > Actually, what I do with them, is a kind of smoothing, as you also propose. > gdalwarp has the ability to resample that data. Even though this does not make > the data "more realistic" of course, moderate resampling can make maps look > much nicer, and usually is not too far off, in my experience. > >> it possible with mapnik symbolizers -- maybe according to zoom levels. >> 2. It seems that I'll have Thousands of Tiff-files for maybe two or >> three zoom levels (I hopw I'll be able to create a suitable TFW-Files >> for them); what would you suggest to work with them with mapnik? > > I use gdal_merge.py to merge them into one file; this at least eases handling > (if the individual files are tiled, or part of one file being hidden by > another > is not a problem). > > Altogehter, my workflow concerning raster images looks something like this > (for > source images in EPSG4326 lat/lon projection, and target srs [the one used for > the rendered mapnik map] being spherical mercator): > > gdal_merge.py -v -o <outfile> -ul_lr <left> <top> <right> <bottom> <image1> > <image2> ... > > gdal_translate -of GTiff -co "TILED=YES" -a_srs "+proj=latlong" -projwin > <left> > <top> <right> <bottom> <infile> <outfile> > > gdalwarp -of GTiff -co "TILED=YES" -srcnodata 32767 -t_srs "+proj=merc > +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m > +nadgrids=@null +no_defs +over" -rcs -order 3 -multi -wt Float64 -ot Float64 > -wo SAMPLE_STEPS=101 -tr 30 30 -multi <infile> <outfile> > > I need the Float64-conversion for the really high zoom levels and hill > shading, where height-differences of one meter would create "steps" instead of > elevation gradients. Actually I am not sure anymore, why I introduced the > middle step (gdal_translate), but as this works fine, I do not have an > incentive to change my workflow just now ... > > Yours, > -- > Holger Schoener [email protected] > _______________________________________________ Mapnik-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/mapnik-users
