osm grey city area

Question

Hello, I need to get cities boundaries, I know how to do it by query the planet_osm_polygon table and get the exact result as in www.openstreetmap.org but its differ from the real city area as marked in grey

e.g Towcester: https://www.openstreetmap.org/relation/1641604

As it can see the area marked in orange is much bigger than the city area

Answer 1

Thanks all for the great info, after some digging I found the way to do what I need.

The purpose is to find the residential boundaries of a given settlement (city, village). for my purpose a farm or few houses alone is not urban so I don't need it

So here are the steps I done, if someone will need it also:

-- 1. find the polygon of the city/village (actually I already have the osm_id of the village in my DB, but to complete the explanation ...) This returned a polygon that include the village but a lot of open areas around it.

select name, osm_id from planet_osm_polygon where name = 'Buckland'

-- 2. get id of the relation(s) that are inside the polygon, need the items with negative osm_id

select i.osm_id, i.name, i.landuse 
from planet_osm_polygon i join planet_osm_polygon o on ST_Contains (o.way, i.way) 
where o.osm_id = -4108597 and i.landuse = 'residential' and i.osm_id < 0

-- 3. get the outer way from planet_osm_rels table

select * from planet_osm_rels where id = 1369487;

-- 4. get the nodes from planet_osm_ways

select * from planet_osm_ways where id = 94437443;

-- 5. get the way's nodes data of the from node table

select * from planet_osm_nodes where id = 1096978061;

I checked it on few locations and its seems to work, of course need to rewrite the queries more efficiently.

osm grey city area

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