[OSM-dev] Extra-large metatiles

Paul Norman penorman at mac.com
Mon Jan 15 02:51:46 UTC 2018

I'm working on a script to do some pre-rendering of a Mapnik-based tile 
layer. Conventional meta-tile sizes would be 4x4 or 8x8, but these are 
selected to balance latency and throughput or efficiency. I'm using 
mapproxy, which stores the tiles as individual files on-disk, not 
mod_tile, which stores metatiles. This means that I can easily change 
meta-tile size, and I don't even have to worry about differing latency 
from slicing PNGs.

Latency does not matter with a pre-render task, so I've been considering 
using extra-large metatiles. Has anyone tried this before?

Based on experience from metatiles 1-8 tiles across, 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.

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.

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