OpenStreetMap

Wierd stuff with the rendering

Posted by Jopparn on 19 September 2012 in English (English)

The coastal line next to Dalkarlså in Northern Sweden look different when you are in edit mode and when you look at the rendered map, which look really stupid. See http://www.openstreetmap.org/?lat=64.0404&lon=20.8938&zoom=14&layers=M

Does anyone have an idea why?

Location: Kyrkvägen, Dalkarlså, Robertsfors, Västerbottens län, Norrland, Sweden

Comment from AE35 on 19 September 2012 at 22:20

Hi

You will find the answer here https://help.openstreetmap.org/questions/276/why-do-the-changes-i-have-made-to-coastline-not-appear-on-the-map

It's because costal line are only rendered after a couple of weeks - So it's not an error you see

best regards AE35

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Comment from LivingWithDragons on 19 September 2012 at 22:22

It might just be out of date and hasn't triggered to be rerendered. There is a trick you can do to make it rerender, mark the tile as dirty by reading these instructions. http://wiki.openstreetmap.org/wiki/Slippy_Map#Mapnik_tile_rendering

Rendering is the process of turning the vector data into raster image tiles. Image tiles look nicer and are easier to load lots of for lots of people, so much more suitable for the 'view' map.

When changes are made, the area should be rendered again. Sometimes that can take up to 2 hours, or a day in unusual circumstances. If it doesn't get put in the list to rerender, then it will do it if you look at the area at least 7 days later. There is also the possibility that your browser is caching the images.

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Comment from Jean-Marc Liotier on 20 September 2012 at 11:03

Even when marking tiles as dirty, coastline rendering is a special case due to the huge size of the natural=coastline ways : coastlines are created using shapefiles generated from the natural=coastline ways by the Coastline Error Checker - that does not happen as often as normal Mapnik rendering, so the coastline's rendering might remain out of date for a long time while the rendering of other objects has already been updated.

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Comment from Jopparn on 20 September 2012 at 11:26

Hello and thank you for your comments.

However, I made the changes more than two weeks ago, and it still does not look okay. Indeed it never actually looked like the rendered version before I started adjusting the coast line. Also, in the area that I linked to there are also trails and roads next to the coast line (I also edited them around three weeks ago) and they are also in the wrong place when the map is rendered, but look fine in edit-mode.

I have checked this area on three different computers now and the same problem appears on all of them (i.e. strange coast line and roads in the water). Here is a closeup of one affected area: http://www.openstreetmap.org/?lat=64.04413&lon=20.90416&zoom=16&layers=M

Any other ideas what might be the problem?

Cheers,

John

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Comment from pieleric on 20 September 2012 at 14:02

Sometimes the changes in the map are not detected by the renderer. You can force it by adding /dirty after the url of a tile. I've just done this, and I think it's now fixed for each zoom level (you still need to refresh the page in your browser).

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Comment from AndrewBuck on 21 September 2012 at 14:51

@Jopparn

The coastline rebuilding does not happen automatically every two weeks, but rather it happens manually whenever the admins get around to running it. Recently there have been a lot of changes to the project happening and so coastline rendering has fallen by the wayside.

Just keep making your changes and they will eventually get shown on the map. I do a lot of coastline work myself and it gets frustrating sometimes as it takes a while to show up but you learn to live with it. (There was about a 4 month gap before the last coastline rebuild) As long as it looks right in the editor then you have done what needs to be done and the update process will happen eventually.

-AndrewBuck

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Comment from AndrewBuck on 21 September 2012 at 14:56

Oh, by the way, just to clear up some info from above, adding /dirty to the tile URL does force a re-render of the tile. But the coastlines shapefiles are built using a separate process as mentioned, and it is these files which are out of date, so re-rendering the tile will update all the roads, etc, in the tile, but the coastline will still look the same until the shapefiles are rebuilt by the admins.

-AndrewBuck

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