Hi Iain After much playing I resorted back to using ImageMagik and setup a loop through all the files and apply a constant blend of the two files(topo and hillshade)
As you mentioned I then re-added the projects using gdal_translate and a world file. I totally agree, support for BIGTIFFs is very low which is a shame when you think about the quality of imagery and other datasets now becoming avaliable. I am surprised how complex the options are, when I set out I thought this would be relatively easy ;) thanks again Tim On 22 February 2012 02:05, Iain Malcolm <[email protected]> wrote: > 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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