On Thursday 04 June 2009 19:48:30 you wrote: > 2009/5/31 Frederik Ramm <[email protected]>: > > Hi, > > > > Tels wrote: > >> Well, one could fetch the data at z17, see it is below some > >> $ARBITRARY_THRESHOLD, zoom out to z16m, fetch again, and if still > >> below $THRESHOLD, repeat it until either there is too much data > >> (display message) or the user-requested zoomlevel was reached. > > > > I think the ti...@home folks already keep a database that says how > > complex each level-12 tile is. So if we were not so busy telling > > them how they're technologically backwards and how their whole > > project is rubbish, they might just give us that. > > Each t...@h user uploads a tileset at z12, which is indeed a pretty good > indicator of the complexity of the area, see this heatmap rendering > of the world at z12 from the t...@h data: > > http://u.nix.is/~avar/osm-heatmap-black.png > > I made if after requesting the z12 tileset sizes on the t...@h list: > > http://lists.openstreetmap.org/pipermail/tilesathome/2009-May/005859. >html > > The code to generate it is under applications/rendering/tah-heatmap > in SVN: > > http://trac.openstreetmap.org/browser/applications/rendering/tah-heat >map/README > > In particular the parse-filesize.pl script in that directory converts > ls -R format provided by spaetz to an easy-to-use CSV format, e.g.: > > 0000,1042 158211 > 0000,1043 203915 > 0000,1055 172469 > 0000,1056 80728 > > t...@h currently has around a million z12 tiles, or ~5.6% of potential > z12 tiles: > > $ wc -l tile-sizes.dat > 937254 tile-sizes.dat > > It would be easy to make a web service which kept these tile sizes in > a hash table and told e.g. Potlatch whether or not the z13 tile it's > requesting is part of a z12 area that's say 10 times bigger than the > median z12 tile. Which should cover the yellow/read areas on the > above heatmap.
If such a webservice is made public, I could use it to determine wether an area of 0.1° or 1° should be requested. However, getting a server that can respond to API requests in real-time (e.g. saturate the download link) would be the preferable situation - after all, all the data needs to be downloaded for rendering, anyway. (Rendering only half the area the user wants to see is useless :) All the best, Tels -- Signed on Thu Jun 4 21:36:19 2009 with key 0x93B84C15. Get one of my photo posters: http://bloodgate.com/posters PGP key on http://bloodgate.com/tels.asc or per email. "I live the way I type; fast, with a lot of mistakes." -- Unknown
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