Dans OpenStreetMap (OSM), une relation est un moyen de regrouper plusieurs éléments, tels que des nœuds, des chemins et d'autres relations, afin de créer une représentation plus complexe et plus significative d'une entité géographique.
For example, a road network can be represented as a relation that groups together individual ways (segments of roads) to create a complete network. Similarly, a river system can be represented as a relation that groups together individual ways (segments of the river) to create a complete network.
Relations can also be used to represent other types of features, such as public transit routes or hiking trails. For instance, a public transit route can be represented as a relation that groups together individual ways and stops to create a complete route. Similarly, a hiking trail can be represented as a relation that groups together individual ways and points of interest to create a complete trail map.
Relations in OSM are identified by a unique ID number and can be created and edited using OSM editors such as JOSM or iD Editor. They are a powerful tool for creating complex and detailed representations of geographic features, and they allow OSM data to be used in a wide range of applications, from navigation tools to disaster response systems.
In summary, relations in OpenStreetMap are a way to group together multiple elements to create more complex and meaningful representations of geographic features. Examples of relations include road networks, river systems, public transit routes, and hiking trails.