Nick, This has been on my list of things to do for a while too, but like many of my project ideas, it didn't get that far! I do not have any experience of the OS contour files - I coudn't work out how to convert the dxf's into something more useable by mapnik (I quite fancied getting them into postgresql like I did with srtm data). I think the OS height data comes as a DEM as well as a DXF so it should be possible to process it like SRTM?
I did have a similar issue with rendering the Vector Map District data though, which comes as lots of shapefiles. I tried it two different ways: 1. Render each shapefile individually using mapnik, by writing a python script to add a different mapnik layer for each shapefile - this worked fine for a single grid square (e.g. NZ), but it keeled over when I tried to do it for the whole UK - ran out of memory I think. 2. Pull the shapefiles into a postgresql database and render it just like OSM data - lines and points worked fine, but I had trouble with polygons - lots of errors about invalid geometry. This was a shame because the big thing I like about VMD is the area data. It looked as though the problem was areas intersecting themselves, but I never worked out how to fix it - I suspect that it may be rounding errors and I should have used the shp2pgsql option to just use integers, but I think I must have got bored before I tried re-importing the entire database again. I made some notes as I went along, which you should be able to see here<http://nerdytoad.blogspot.com/search/label/OrdnanceSurvey>. The scripts I wrote and mapnik stylesheets are in a public archive, which should be referenced in my notes. I suspect that you will have a similar problem with the contour shapefiles as I had with the VMD ones, so I would be inclined to go for the database option, or at least treat that as a contingency plan. I would like to see this idea working, so if you would like any help, please let me know. Regards Graham. On 6 March 2011 09:11, Nick Whitelegg <[email protected]> wrote: > Hi, > > Sometime, perhaps over Easter, I'd like to do something I've been meaning > to do for a while, and that is create "pseudo-Landranger" maps by combining > OS Vector Map District, contours from OS Landform Panorama, and OSM > footpaths. > > However, to do this I need to transform the contour data from DXF into > something more usable, e.g. shapefile. Apparently gdal can now do this. > What I'm a little concerned about, though, is the viability of creating one > huge shapefile containing all the contours for the UK, which would be > necessary to prevent the Mapnik XML file getting messy and having huge > numbers of small shapefile layers. As an alternative I could create separate > shapefiles for say, Wales, S England, N England and Scotland. > Is this likely to be feasible. > > Thanks, > Nick > > _______________________________________________ > Talk-GB mailing list > [email protected] > http://lists.openstreetmap.org/listinfo/talk-gb > > -- Graham Jones Hartlepool, UK.
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