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Hi, it might exist some relevant answer for my question but I haven't found any so I allow to ask another one :-) I did some changes in openstreetmap through JOSM. These changes were visible almost immediately but only in higher zoom. In the lover zoom there was visible only the old state (without added roads, old types of roads...) What did I wrong? lower zoom:
higher zoom:
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You didn't do anything wrong. This is the normal behaviour of the map rendering process. Recalculating low zoom tiles is a relatively resource expensive operation. As a low zoom tiles covers a relatively large area, chances are that something changes in the area every minute. As the rendering process cannot determine if it is a relevant change ahead of time, it would have to re-render those low zooms very frequently. As rendering can take several minutes for low zoom, re-rendering the tiles on every change is clearly not feasible. Furthermore, most changes (e.g. moving a building by half a meter) do not cause visual changes on low zoom. At least in well mapped areas, these non visible changes at low zoom are likely the vast majority. Therefore, the system separates the rendering process into low zoom and high zoom tiles. (I can't remember at which zoom level the switch is). The high zoom tiles get expired on a minutely basis (if the data in their area changes) and will therefore get rerendered quickly once viewed. Low zoom tiles are not re-rendered based on changes in the map data. Instead they are periodically re-rendered in full. Again, I don't know what this current update cycle is but it can be a week or longer. If you know an area has changed and it has caused a noticable visual change in low zoom tiles, you can manually request a rerender of those tiles. This is done by right clicking on the area in the map and selecting "copy image URL". This should give you a URL like http://b.tile.openstreetmap.org/11/1286/782.png Then you can request a rerender by opening the URL http://b.tile.openstreetmap.org/11/1286/782.png/dirty After a couple of minutes to an hour, you should see your changes on that tile as well. A more detailed description of the process can be found in this answer. thanks for excellent explanation. The link above helped me to comprehend this as well.
(05 Feb '13, 19:02)
milda_brno
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There's sometimes a short delay before the update of the main map, as described in this answer, which also explains how to speed the process up. Some of the new roads are now visible at higher zoom too. |
That's roughly here I think...