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My question is about processing raw OSM data from .osm.pbf exports.

Please don't point me to any online tools, nominatim, or overpass queries.

I have list of Nodes that represent cities in all Europe, for example node for Wrocław has ID of 418392093

I'd like to select from .osm.pbf relation that represents boundary of this city. Fortunately, boundary=administrative Relation has Wrocław's ID listed as admin_centre. Unfortunately Wrocław is also listed as admin_centre of the region it is in (Dolnośląskie voivodeship).

How can I know for sure which boundary relation matches which city node?

Subquestions:

  1. If the answer is "you can use name", is it reliable method? Does boundary has always the same name as node?
  2. If the answer is "select boundary with highest admin level", is it reliable as well? What if subregion has the same admin centre?
  3. If there isn't "official" method of doing so, why? It seems an important use case to know boundary of any city.

Raw data for Relation for administrative boundary of Wrocław city looks like this:

  {
    "ID": 2805690,
    "Members": {
      "admin_centre": [
        418392093
      ],
      "outer": [
        52452667,
        ...
        443264980
      ],
      "subarea": [
        2341621,
        ...
        2318980
      ]
    },
    "Tags": {
      "admin_level": "8",
      "boundary": "administrative",
      "name": "Wrocław",
      ...
      "name:szl": "Wrocłow",
      "old_name:eo": "Breslaŭo",
      "old_name:pl": "Wratislaw",
      "type": "boundary",
      "wikidata": "Q1799",
      "wikipedia": "pl:Wrocław"
    }
  },

Raw data for Relation for administrative boundary of a region Wrocław is in looks like this:

 {
    "ID": 224457,
    "Members": {
      "admin_centre": [
        418392093
      ],
      "label": [
        505025705
      ],
      "outer": [
        175469910,
        ...
        176467203
      ],
      "subarea": [
        451266,
        ...
        451516
      ]
    },
    "Tags": {
      "ISO3166-2": "PL-DS",
      "admin_level": "4",
      "alt_name:en": "Lower Silesian Province",
      "boundary": "administrative",
      "int_name": "wojewodztwo dolnoslaskie",
      "license_plate_code": "D",
      "loc_name": "Dolnośląskie",
      "long_name:fr": "Voïvodie de Basse-Silésie",
      "name": "województwo dolnośląskie",
      "name:ar": "محافظة سيلزيا السفلى",
      ...
      "name:zh": "下西里西亚省",
      "population": "1970217",
      "ref": "DS",
      "short_name": "dolnośląskie",
      "source:population": "Bank Danych Lokalnych - stan na dzień 31.12.2016",
      "teryt:terc": "02",
      "type": "boundary",
      "wikidata": "Q54150",
      "wikipedia": "pl:Województwo dolnośląskie"
    }
  },

asked 10 Aug '18, 17:37

sheerun's gravatar image

sheerun
10113
accept rate: 0%

edited 10 Aug '18, 17:38

At a minimum you need to create geographical objects from your PBF. It so happens Nominatim & Overpass are by far and away the easiest options. You cant process relationships in geodata without turning into geographies. A short answer is process into PostGIS with osm2pgsql and write suitable queries there: the downside is that you lose some explict relationships between city nodes & boundary relations: however as there is no guarantee that these exist consistently you still have to solve the problem.

(10 Aug '18, 22:10) SK53 ♦
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question asked: 10 Aug '18, 17:37

question was seen: 1,516 times

last updated: 10 Aug '18, 22:10

NOTICE: help.openstreetmap.org is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum