[OSM-dev] My Maps Appear to be Predicting Global Warming.

Jon Burgess jburgess777 at googlemail.com
Fri Feb 19 18:59:10 GMT 2010

On Fri, 2010-02-19 at 14:40 +0000, Richard Ive wrote:
> On 19 February 2010 14:24, John Smith <deltafoxtrot256 at gmail.com>
> wrote:
>         On 19 February 2010 22:01, Lennard <ldp at xs4all.nl> wrote:
>         > The one major cause of flooded tiles is when mapnik doesn't
>         process the
>         > coastline shapefiles. At z10, it switches from the lowzoom
>         shoreline_300
>         > to the full resolution processed_p shapefile. So focus your
>         effort on
>         > that one.
>         Also these shape files are only updated intermitently, so even
>         if you
>         make a change to fix problems with coastlines it might take
>         weeks or a
>         month before the changes will be reflected in OSM tiles.
> Sorry guys, not sure I'm following here.
> I understand what you mean by shape files, but I haven't changed
> anything on the server at all in the 3 months I've had it up and
> running. The only thing that has changed is the database, because I
> import daily change sets into the gis database and even that is on a
> completely different physical machine. Why should my tiles be
> affected, but osm.org's not?
> Cheers for the replies so far! Hopefully I'll catch on soon.

Do all the high zoom tiles have the same issue or just a subset?
Are you running on a 32 bit machine or using a 32 bit renderd process?

Since the shapefiles are quite large it is possible that you run into 
problems with running multiple rendering threads in parallel. Mapnik
tries to mmap() the file in each rendering thread and will quickly run
out of space in a 32 bit process. Try running with a lower "-n" value,
perhaps try just 1 to start with, then only one thread will be actively
rendering at a time.

Most modern multi-core systems will run a 64 bit OS and do not have this


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