Open Street Map - Data Format

Data Format

OpenStreetMap uses a topological data structure, with four core elements (also known as data primitives):

• Nodes are points with a geographic position, stored as coordinates (pairs of a latitude and a longitude) according to WGS 84. Outside of their usage in ways, they are used to represent map features without a size, such as points of interest or mountain peaks.
• Ways are ordered lists of nodes, representing a polyline, or possibly a polygon if they form a closed loop. They are used both for representing linear features such as streets and rivers, and areas, like forests, parks, parking areas and lakes.
• Tags are used to store metadata about the map objects (such as their type, their name and their physical properties). A recommended ontology of map features (the meaning of tags) is maintained on a wiki.
• Relations are used for representing the relationship of existing nodes and ways. Examples include turn restrictions on roads, routes that span several existing ways (for instance, a long-distance motorway), and areas with holes.