[OSM-dev] [Talk-GB] Viability of huge shapefile of LandForm Panorama contours in Mapnik?

Nick Whitelegg Nick.Whitelegg at solent.ac.uk
Sun Mar 6 12:20:48 GMT 2011



>Nick,
>This has been on my list of things to do for a while too, 

Same with me, but it's never been the no.1 priority, hence it's never really seen the light of day yet. Maybe the next rainy weekend we get I'll do a concentrated push at it...

>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? 

Yes, in fact I myself made it available a few weeks ago (see talk-gb post from, I think, early to mid Feb). This suits one of my other projects (in fact my main interest right now) - an
augmented reality based Android app - but a DEM isn't really much different to DXF as far as importing into Mapnik goes. There is the standard cyclemap SRTM to PostGIS tool
chain, but the code to convert SRTM to GeoTIFF contains stuff I don't fully understand so thought going via the shapefile route would be less fuss as I know that GDAL can now
convert DXF to shapefile. Maybe using GDAL to convert DXF to postgis is a possibility - I need to look into this.

>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:
>I made some notes as I went along, which you should be able to see here.  The scripts I wrote and mapnik stylesheets are in a public archive, which should be referenced in my notes. 

OK, thanks for that. 
>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'll probably investigate the possibility of using GDAL to go straight from DXF to PostGIS initially, or if that doesn't work, write my own DXF->PostGIS but with limited time that's not ideal.

>I would like to see this idea working, so if you would like any help, please let me know.

Thanks. 

Nick

 

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