[Tilesathome] [OSM-dev] Proposal for T at H land/sea updates

Dirk-Lüder Kreie osm-list at deelkar.net
Tue Jun 3 14:12:55 BST 2008


Alan Millar schrieb:
> I'd like to make a proposal for improving Tiles at Home.  Before anyone asks,
> yes, I am volunteering to code this.  I'm looking for clarification,
> feedback, or suggestions.

Sorry Sebastian and I got a bit thin-skinned but the amount of well 
meant but resource consuming suggestions was a bit much over the last 
days/weeks. Thanks anyway for really wanting to contribute.

And also thanks for taking *your* time to try and understand how it 
works currently, and explain exactly what you want to do, how you 
perceive the problem, why and how you think it should be solved. This 
makes it real fun to answer your questions.

> The problem with this is that this data is distributed as part of the
> code.  The file can be updated and recommitted to svn, but areas will be
> rendered incorrectly until every t at h client gets every update.

This is in the process of being fixed, but one dependency less would 
probably be a good idea, Especially since moving this big binary file in 
and out of svn probably isn't the most efficient way to do it.

I'm not repeating what Sebastian told you, to keep it short, and save a 
bit of your time.

> It should not affect the performance of close_areas.pl by much, since it
> only needs to retrieve one tile (or 9 tiles if a miss).

I think it's only 5, the diagonal tiles are not consulted IIRC.

> The big advantage of this method is that anyone can fix a tile without
> needing developer svn access, and without requiring renderers to
> constantly update their code.  It only requires a moderate change to
> close_areas.pl and the creation of one new layer, and doesn't impact the
> rest of the process.

There is also the update mechanism via informationfreeway.org at z12, 
but I am currently not sure who maintains the updating of oceantiles.dat 
from there.

Another thing: basically close-areas.pl doesn't really need other 
information than sea/land, because if the tile is coastal, it will know 
by the coastline entering and leaving the tile. Basically all that's 
interesting to close-areas.pl is: do we need to make a coastline-way 
around the tile to render and create islands inside, or do we treat 
closed coastlines as "lakes"?

-- 

Dirk-Lüder "Deelkar" Kreie
Bremen - 53.0952°N 8.8652°E


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