Relation:site

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Public-images-osm logo.svg site
Mf Relation.svg
Description
A site relation is used to group several objects together. Edit this description in the wiki page. Edit this description in the data item.
Useful combination
Wikidata
Status: in usePage for proposal

A site relation is used to group several objects which cannot be adequately described by an area or a multipolygon. The group as a whole should have a common name and other common characteristics.

This relation is not to be used in cases where the element can be represented by one or more areas and neither linear ways nor nodes outside these areas would have to be included or excluded from within these areas. For example the tag amenity=school describes the perimeter of the school grounds, for schools with multiple sites the multipolygon relation should be used. For an university with sites scattered throughout the city, a multipolygon amenity=university with the buildings as role outer should be used.

The features should have a close geographic relationship, usually within the same town. For example do not use this relation to group all restaurants of a fast-food chain. Use a a combination of name=*/operator=*/network=*/brand=* to group loosely coupled and/or widely distributed features - relations are not categories!

See the proposal page for more context and examples.

How to Map

Create a relation and add type=site. In addition, the relation must have a main tag defining whatever feature the site relation describes. E.g. amenity=university, site=parking, site=piste, power=plant, ...

To the characteristics all necessary tags are added:

Sometimes the tag site=* is used to further specify the kind of site, with values such as geodesic, stop_area, parking, wind_farm, mall, piste, etc. However, most of these values have not been documented.

Then the members are added without having to specify a role.

Members may include nodes or ways.

Problems

Sometimes other relations, especially multipolygon relations, have been added as members of a site relation. This can be difficult for database users to interpret, so it should be avoided where possible.

In many cases standard solutions, for example multipolygon relations, are a perfectly acceptable replacement.

Site relations are typically not interpreted or used by database users such as map rendering or routing applications or any other software, unlike for example multipolygons that have obvious meaning, standard form and widespread support. But it is possible to support also site relation[1]

Currently, 50% of the uses of the tag type=site are from an import from the source "©IGN 2010 dans le cadre de la cartographie réglementaire" in France, combined with the tag site=geodesic, to relate groups of man_made=survey_point features.

Another 28% of uses were imported with site=stop_area for public transportation features in Germany, with the source tag "naptan_import". Such public transportation stop area features are now more commonly tagged as type=public_transport relations plus public_transport=stop_area.

See also

  • https://github.com/yvecai/mapnik-opensnowmap.org/blob/master/pistes-carto/project.yml#L1126