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When I search "Taiwan Strait" ( ), the correct multipolyon result (, 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 '21, 22:51

strongwillow's gravatar image

accept rate: 0%

edited 11 Apr '21, 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 '21, 00:06

Frederik%20Ramm's gravatar image

Frederik Ramm ♦
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: It's a rough approximation but it's good enough for different purpose

(12 Apr '21, 09:31) strongwillow

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 '21, 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 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 '21, 23:06

mtmail's gravatar image

accept rate: 27%

Thanks for checking. Indeed large multipolygon tends to break

(12 Apr '21, 09:24) strongwillow

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question asked: 11 Apr '21, 22:51

question was seen: 1,387 times

last updated: 12 Apr '21, 11:03

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum