[Talk-GB] London progress

Dave osm.list at randomjunk.co.uk
Wed Apr 18 14:33:45 BST 2007


> > There's some really cool mapping going on. The coverage has more than
> > doubled, and there's loads of interesting details appeared such as
> > heathrow airport and just about every railway line there is!
>
> Does this include the underground?  How do you get traces for that?
>

It includes it where people have tagged the lines as railway=subway.
I think it's about two thirds of the tube that is actually above
ground: GPSs work fine on District line trains at least, and besides
which you can easily see the lines from Yahoo aerial imagery.
In parts of london I think some people have made heroic attempts at
mapping lines based on joining the stations together :-(
With the cut and cover lines you can often see the route on the aerial
imagery even when it is below ground.


> > If anyone is interested as to what it takes to render these images
> > (they're done in one go, not stitched together from tiles):
> >
> > value in October -> value now
> > .osm file size:  33MB -> 75MB
> > .svg file size: 65MB -> 140MB
> > CPU time (2.8GHz P4) 35 mins -> 2 hours 40 mins
> > memory: 900MB RAM -> 1.6GB RAM + 250MB swap
>
> Do you save out the data from josm, or have some way to query the database
> and get data from different dates?
>

I have a python script which pulls down the data in tiles from the
server and then concatenates the files together (not a neat merging
technique, but osmarender doesn't seem to care). The script is on my
user page on the wiki, although most of the rest of that page is out
of date:
http://wiki.openstreetmap.org/index.php/User:Randomjunk




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