Tim, mapnik is only sensible if you are aiming to end up with tiles anyway, which from what you said now is not the case. It isn't the right tool if you want single large output files.
gdal copes well with large files (I have used with single files up to 11Gb, but you do need a reasonable amount of memory in your PC. (2Gb or more) It could well be a good idea to do the preliminary work on the smaller files you mention, and then combine them, but you may end up with edge problems with this approach. Are these input files SRTM data by any chance? I produced contour coloured and hillsahded files for the british isles by merging with gdal, then using hillshade etc. to generate the relevant output files. >From what you have said it sounds like you have produced a file with the data you want in it, but because it lacked the geo bits it was no use, but you can put the geo info back into a tiff, or perhaps use a sidecar style file, although I haven't done that myself,I have seen mentions of it in my geotiff travels. Also note that many applications will not handle very large tiff files. The original tiff spec has been extended and not many tools have picked this up yet - (although gdal is one that has). Original tiff only worked up to around 4Gb. See this fo<http://trac.osgeo.org/gdal/wiki/FAQRaster#HowtomakeGeoTIFFfromnon-geospatialraster>r how to get GDAL to put the geo back into a tiff The best approach does depend on what tools / applications you finally want to use this info with. It would be helpful if you could briefly describe what your end goal is. Iain On 21 February 2012 15:07, tim martin <[email protected]> wrote: > Hi > > I have been recommended to use Mapnik to combine two geotiffs, one > topogrpahic and one hillshade. > > I have managed to do this using an XML mapfile and a short python script, > just like in the tutorials. > > However, I need to create a geotiff output of 132000 by 248000 pixels, > even going above 6000 by 6000 i get an out of memory error. > > So the other way I think I could do it is run the geotiff+hillshade on the > smaller original geotiffs which are 4000 by 4000 each. > > However there are 2000 of them so how can I program mapnik to step through > each one rather than write 2000 entries in my map.xml file > > thanks for your help > > Tim > > _______________________________________________ > Mapnik-users mailing list > [email protected] > https://lists.berlios.de/mailman/listinfo/mapnik-users > >
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