Overpass turbo/Polygon Features
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As OpenStreetMap doesn't have an intrinsic area data type, an heuristic has to be applied to determine whether a way is a Line or a Polygon. For Overpass turbo and osmtogeojson I came up with the following (see here for a machine-readable JSON file of this table):
A way is considered a Polygon if
- It forms a closed loop, and
- it is not tagged area=no, and
- at least one of the following conditions is true:
- there is a area=* tag;
- there is a area:highway=* tag and its value is not: no;
- there is a aeroway=* tag and its value is not any of: no, or taxiway;
- there is a amenity=* tag and its value is not: no;
- there is a barrier=* tag and its value is one of: city_wall, ditch, hedge, retaining_wall, wall or spikes;
- there is a boundary=* tag and its value is not: no;
- there is a building:part=* tag and its value is not: no;
- there is a building=* tag and its value is not: no;
- there is a craft=* tag and its value is not: no;
- there is a golf=* tag and its value is not: no;
- there is a highway=* tag and its value is one of: services, rest_area, escape or elevator;
- there is a historic=* tag and its value is not: no;
- there is a indoor=* tag and its value is not: no;
- there is a landuse=* tag and its value is not: no;
- there is a leisure=* tag and its value is not: no;
- there is a man_made=* tag and its value is not any of: no, cutline, embankment nor pipeline;
- there is a military=* tag and its value is not: no;
- there is a natural=* tag and its value is not any of: no, coastline, cliff, ridge, arete nor tree_row;
- there is a office=* tag and its value is not: no;
- there is a place=* tag and its value is not: no;
- there is a power=* tag and its value is one of: plant, substation, generator or transformer;
- there is a public_transport=* tag and its value is not: no;
- there is a railway=* tag and its value is one of: station, turntable, roundhouse or platform;
- there is a ruins=* tag and its value is not: no;
- there is a shop=* tag and its value is not: no;
- there is a tourism=* tag and its value is not: no;
- there is a waterway=* tag and its value is one of: riverbank, dock, boatyard or dam;
This is mostly based on the information found in the OSM-wiki (namely the presence and absence of the / symbols on the individual key-pages). I used taginfo's wiki database for this task.
Unfortunately, the wiki doesn't include any information about whether or not a tag is categorizing (such as landuse=*) or descriptive (such as name=*). Therefore, this heuristic includes my own understanding and opinion about this. For the same reason, this list is surely quite incomplete! Please inform me about more tags that could imply areas.