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Author Topic: OpenStreetMap - some technical bits  (Read 523 times)

PeterC

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OpenStreetMap - some technical bits
« on: 24 February 2016, 20:52:49 »
The Elements of OSM are
  • A Node is a single point in space (defined by its latitude, longitude)
  • A Way is an ordered list of nodes which also has at least a tag, or is in a relation, (it usually defines a linear feature or an area boundary)
  • An area (or filled polygon) is a filled closed way - it is not a data primitive like the others
  • A Relation is used to model logical (and usually local) or geographic relationships between objects (members of a relation can have "roles")
A Tag consists of a 'Key' and a 'Value'. Each tag describes a specific feature of a data element, eg for a way it could be highway=residential. The details of Features and Tags is a full reference, and you can find more in TagInfo.

The article on Getting source data from OpenStreetMap is useful. And the interactive environment for querying OSM and seeing the results on the map (Overpass turbo - and its wiki article) it mentions is very useful, particularly for seeing all the features and their tags.

Notes on Overpass turbo: If you just enter type:way, you will get all lines and outlines. If you just enter type:relation, you will probably get a huge number of nodes of boundaries. To get all buildings you could enter building=*.

This application was built to enable a quick overview and import of existing open data into OpenStreetMap.
« Last Edit: 2 January 2017, 06:58:13 by PeterC »

 

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