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Public-images-osm logo.svg place = sea
Envisat image over the Red Sea ESA209860.jpg
A part of an ocean. Show/edit corresponding data item.
Group: places
Used on these elements
may be used on nodesshould not be used on waysmay be used on areas (and multipolygon relations)should not be used on relations (except multipolygon relations)
Useful combination
Status: in usePage for proposal

A large body of marine water and part of an ocean: seas, gulfs such as the Gulf of Mexico, bights and very large bays such as the Bay of Biscay and Bay of Bengal.

Note that oceans are mapped separately, see place=ocean.

How to Map

Add the place=sea to a node near the center of the marine water body.

Same as with other features which do not have the one local name, enter names in official languages of all surrounding countries or leave the tag name=* empty. Fill the tags name:code=* (where code is ISO 639 code of the language) with names in different languages.


Example for the South China Sea:

name=Biển Đông / Dagat Timog Tsina / Laut China Selatan / Laut Tiongkok Selatan / South China Sea / தென்சீனக் கடல் / ทะเลจีนใต้ / សមុទ្រចិនខាងត្បូង / 南海
name:en=South China Sea
name:pl=Morze Południowochińskie

Mapping seas as areas

Originally most seas (including large bays and gulf, such as the Gulf of Mexico and the Bay of Bengal) were mapped as nodes in late 2008: there were about 110 at that time. In 2014 and 2015 about a dozen additional seas were mapped as multipolygon relations. In late 2018 and early 2019, a number of sea nodes were deleted and large multipolygons were created instead. This is controversial, because most seas do not have verifiable boundaries with the open ocean or other seas. Also, such large multipolygon relations can be very difficult to maintain; they must be edited whenever the coastline is split or merged or a new island is created, and thus can be easily broken. For these reasons mapping seas as areas with multipolygons is controversial.

Note that oceans are always mapped as nodes, and most bays are mapped as nodes (There are 47,000 bay nodes vs 7,000 bay ways and relations as of mid 2019).

The trend to map seas as multipolgyons is related to the increase in mapping bays and straits as multipolygons, which also became more common at the same time, most likely due to a controversial change in rendering by the OSM Carto style sheet, the style used by the standard map layer on openstreetmap.org. However, note that seas are not rendered by that style as of mid-2019.

Maps showing seas

See also