[OSM-dev] Extra-large metatiles

[Hartmut Holzgraefe]

Based on experience from renderinging large areas for print via my
MapOSMatic clone:

> as size increases I 
> expect query time and time to render to increase, but time per tile to 
> decrease. I don't know at what point this stops being true.

PostGIS Query time seems to go up in a non-linear fashion with the area
to reander. This is just a gut feeling so far though, I did not get to
really benchmark this yet.

> I believe Mapnik has problems with very large images, but I'm not sure 
> when that happens. I think at least 16k px wide is doable.

At least with the Cairo backend the limit is hard coded at 32k (or 30k 
already). I can't use AGG in my setup as additional content gets added
via pyCairo, so I don't know what limits that may have.

-- 
hartmut