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

Richard Ive richard at xanox.net
Fri Feb 19 09:29:01 GMT 2010


Hi All,

Sorry for sending this twice, I believe the attachment was too big last
time?

I seem to have a problem with mod_tile / mapnik ect predicting global
warming in the UK.

Before I start to explain, please see the following links.

http://maps.4d.m4.net/osm_tiles2/10/513/334.png
http://maps.4d.m4.net/osm_tiles2/13/4126/2732.png
http://maps.4d.m4.net/osm_tiles2/12/2033/1370.png
http://maps.4d.m4.net/osm_tiles2/12/2034/1352.png


Basically it looks like wherever an inland tile contains water such as a
lake, or river the surrounding tiles all have a blue background, thus making
the land look under water. Everything else still renders on top of this
'water', so roads and buildings are still visible. I have so far been unable
to find a trend in where this appears. The only thing I have noticed is it
appears in zoom levels higher than 10 (by higher I mean numerically higher,
not altitude).

I've had my rendering server running for a good 3 months now, and the only
problem I had with it was that within the last month mod_tile took an age to
return anything, even if the tile was fresh. One thing I did try was to run
render_all which comes with mod_tile because I forgot to add that to a
weekly cron. I slightly modified it to:

#!/bin/bash

for z in `seq 0 18`
do
        (/home/richard/software/mod_tile/render_old -z $z -Z $z -n 4 &>
render.txt) &
done

This solved the speed issue, but also caused the 'flooding' - I assume.

If you need any further details please ask.

Thanks for you help in advance.

-- 
Regards,
Richard Ive.
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