Hello,

When I search "Taiwan Strait" ( https://www.openstreetmap.org/search?query=Taiwan%20Strait ), the correct multipolyon result ( https://www.openstreetmap.org/relation/9348353, it's a big one so might take a while to load ) does not shown in the result.

I checked the multipolyon in JOSM and it's quite complex one.

Is this a bug in Nominatim or issue in the strait multipolygon?

Thanks in advance!

asked 11 Apr, 22:51

strongwillow's gravatar image

strongwillow
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accept rate: 0%

edited 11 Apr, 22:54


Mapping these bays and straits as multipolygons is error prone (they are easy to break), pollutes the database with countless versions (every time someone splits a pice of coastline, a new version of the relation must be uploaded), creates giant objects that complicate editing for everyone (there is a reason we don't map oceans as polygons...), and serves no purpose that could not equally be served by a node. When I encounter polygons like that, I usually replace them with a node. I have done that here now.

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answered 12 Apr, 00:06

Frederik%20Ramm's gravatar image

Frederik Ramm ♦
76.6k886861186
accept rate: 23%

Hi @Frederik, I also don't like this kind of super large multipolygon for all sorts of reasons. Thanks for confirming this is bad mapping.

However I don't quite agree to replace that with just a node. A strait node is rendered usually insignificantly. How about a simple polygon like English Channel: https://www.openstreetmap.org/way/920269202 It's a rough approximation but it's good enough for different purpose

(12 Apr, 09:31) strongwillow
2

That English Channel polygon is terrible. It doesn't even have holes for the Channel Islands. It will break anything which renders water polygons above land.

(12 Apr, 11:03) Richard ♦

The main polygon looks broken when I inspect with the JOSM editor. All elements (ways) exist but there's two gaps and some ways are not in the correct order. Sadly http://ra.osmsurround.org/analyzeRelation times out for me for this relation, it's huge. Once fixed Nominatim will import it and link the node to the relation (based on position and wikidata id).

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answered 11 Apr, 23:06

mtmail's gravatar image

mtmail
4.3k1465
accept rate: 29%

Thanks for checking. Indeed large multipolygon tends to break

(12 Apr, 09:24) strongwillow
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question asked: 11 Apr, 22:51

question was seen: 164 times

last updated: 12 Apr, 11:03

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