Talk:Overpass turbo/Polygon Features

Name

Shouldn't you mention here that a name=* is needed for a polygon to be an area in Overpass turbo? - redrat

For searching them may be, but I don't think this aplies to all polygons you can retrieve with Overpass queries. Areas can be computed for some categories even if they don't have a defined name, for example ponds or forests (whic hare frequently fragmented using custom or administrative boundaries or some other interal physical boundaries such as riverbanks).

It may even make sense to search for riverbanks even if they are left without names (in one of the various arms of a river). — Verdy_p ^(talk) 18:46, 3 September 2017 (UTC)

Indeed I was searching for leisure= areas, named or not, but I found only named were retrieved by the query. My concern is mainly about documentation though also I don't understand the reason for this. According to [1] actually only named polygons are computed as area. - redrat 19:38, 3 September 2017 (UTC)

Well, there are two different things at play here: One is the list of Overpass areas you can query and use as search filters in an overpass query. The other thing is what tags are used inside Overpass turbo to determine which features should be drawn as polygons rather than closed lines (think of a building versus a roundabout: in OSM both are typically closed ways, so a list of tags is needed to find out how to actually draw them). This page and list of tags was created only for the second use-case.

It is true that Overpass-API uses a very similar list (the one you already found on github), which was originally adapted from this list here. But it is made for a different purpose. And for performance reasons (I think), that list only includes named areas (because otherwise one would end up with too many areas, which can't be processed on the server anymore).

-- Tyr (talk) 09:40, 4 September 2017 (UTC)

historic=yes

historic=yes is not that uncommon (see taginfo), and is currently marking features as polygons, even though in some combinations this might not be the mapper's intent, e.g. on an object like barrier=wall + historic=yes (currently about 2600 times in OSM). It might be worth considering adding the value "yes" to a blacklist for the "historic" tag key. Maybe similar ones as well (historic=railway, …)?

-- Tyr (talk) 10:03, 4 November 2020 (UTC)

How to search for a polygon

With telling users how to search for a polygon using overpass turbo, this page is essentially useless. SomeoneElse (talk) 12:26, 16 January 2022 (UTC)

Hi. I'm not sure I can follow you here. This page just documents a particular detail of overpass turbo's (internal) conversion algorithm from OSM to "GIS" data. What else does it need to be more useful? -- Tyr (talk) 16:05, 17 January 2022 (UTC)

A user searching the wiki about overpass turbo is far more likely to be asking "how do I search for polygons" (or closed ways) than wondering which OSM features Overpass turbo considers polygons and which it does not. I suspect that more people read the OSM wiki trying to answer concrete "how do I..." questions rather than philosophical ones. SomeoneElse (talk) 21:11, 18 January 2022 (UTC)