Hi, can anybody tell me why way 122184832 is visible as a building while the adjacent way 122186232, tagged identically, is not visible on the map (Mapnik renderer)?

Thanks

asked 19 Jul '11, 08:39

Pyrokrat's gravatar image

Pyrokrat
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retagged 19 Jul '11, 14:46

banoffee's gravatar image

banoffee
85441420

Very good question. Osmarender shows them.

(19 Jul '11, 09:35) petschge

Any new info?

(28 Jan '12, 19:54) LM_1

Not yet, the buildings still don't render as of today.

(28 Jan '12, 20:42) Pyrokrat
2

Update one year later: The buildings still don't render.

(28 Jan '13, 07:13) Pyrokrat

I guess uploading a new version of these objects will fix the problem. In JOSM this can be done by adding a tag and removing it again, the object will then be seen as modified and on upload a new version will be created without changing anything. But the actual source of the problem has to be identified in order to avoid further similar issues.

(28 Jan '13, 09:34) scai ♦
2

I switched a tag back and forth on these buildings and now they render. I originally wanted to leave way 122186232 as is to keep an example for the problem but unfortunately I forgot it.

(30 Jan '13, 07:32) Pyrokrat
showing 5 of 6 show 1 more comments

The tiles you see as the "mapnik tiles" are rendered from a secondary database. This secondary database is kept up to date with the primary database via the application of "minutely diff" files. Furthermore, the data is transformed from a representations of nodes, ways and relations into points, lines and polygons.

The program doing this conversion (osm2pgsql) unfortunately has some known bugs under which in edge cases the transformation during the application of diffs is incorrect, leading to some data not being correctly in the secondary database and thus can't be rendered. This then leads to the "invisible buildings"

The likely bug in your case is #4525 ( https://trac.openstreetmap.org/ticket/4525 ). If a way is originally part of a multipolygon and rendered as such, then if it gets removed from the polygon relation, but the way itself remains unmodified, it will be deleted from the database.

For the moment, until the bug is fixed. Touching the individual way (i.e. re-uploading / modifying the way) is currently the only solution to getting the way to render.

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answered 30 Jan '13, 22:48

apmon's gravatar image

apmon
6.2k174456
accept rate: 20%

Thanks for the detailed answer! I think this phenomenon is due to the bug you are referring to. The whole block of buildings was in fact a multipolygon before I broke it down into multiple ways.

(31 Jan '13, 07:12) Pyrokrat

The data looks right and Osmarender shows all the buildings. I guess that there was some problem with the mapnik database excerpt or similar which will be resolved automatically once the rendering server does the next full import and the tiles get rerendered.

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answered 30 Jul '11, 12:19

dieterdreist's gravatar image

dieterdreist
3.6k113466
accept rate: 3%

An update on this: Situation unchanged, I filed it as a bug but they suspected server outage to be the reason. Since I continuously do mapping and my other changes appear immediately, I can almost certainly rule this out. Any other ideas?

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answered 29 Jul '11, 06:54

Pyrokrat's gravatar image

Pyrokrat
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accept rate: 0%

I had looked at it yesterday,what would happen if you deleted a couple of the invisible ones saved it then opened the editor and re drew them. or would downloading the area into josm altering something slightly and uploading again work or have to tried that already

(29 Jul '11, 10:12) andy mackey
1

Redrawing the ways (using the existing nodes) helps but I don't want to remove the issue in case a developer wants to have a look at it.

(29 Jul '11, 12:53) Pyrokrat

ok, thanks explaining that

(29 Jul '11, 15:17) andy mackey
1

My best "wild guess" would be that the time at which the mapnik server got its last full update before/during the maintenance and the time at which it started applying minutely updates to that data were not the same, and that your changes (as well as any other changes throughout the entire world at a similar time) are not reflected in the mapnik copy of the database...

... and that it would go away when mapnik's database is next fully resynchronised - presumably when the "main" server comes back online.

Seems useful to have a known anomaly to see when this occurs.

(01 Aug '11, 12:12) banoffee
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question asked: 19 Jul '11, 08:39

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last updated: 31 Jan '13, 07:12

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