{"id":59,"date":"2020-12-21T12:34:55","date_gmt":"2020-12-21T12:34:55","guid":{"rendered":"https:\/\/mapio.cymru\/?p=59"},"modified":"2020-12-21T16:14:35","modified_gmt":"2020-12-21T16:14:35","slug":"overpass","status":"publish","type":"post","link":"https:\/\/mapio.cymru\/en\/2020\/12\/overpass\/","title":{"rendered":"Fun with Wales’ map data: a tutorial using Overpass queries and OpenStreetmap"},"content":{"rendered":"

Map: places in Wales that have ‘llan’ in their names<\/em><\/p>\n

Would you like to get castles, rivers, post boxes, or cycleways in Wales from a map?<\/p>\n

How about investigating place names in Welsh in your local area?<\/p>\n

How about getting other features in Wales and further afield, as open data from a map?<\/p>\n

This blog post will show you how to get open data from OpenStreetMap, with a particular emphasis on Welsh-language data.<\/p>\n

It is intended as a fun introduction, not as a comprehensive reference guide. No previous experience is necessary.<\/p>\n

We will be passing queries to the Overpass API, and it’s easy to get started. The queries can be run from your web browser in Overpass Turbo<\/a>, which is one seriously cool app. Other than that your curiosity is the only prerequisite!<\/p>\n

Introductory concepts<\/h2>\n

Feel free to skip this section if you want to head to the practical bit straightaway.<\/p>\n

OpenStreetMap is a global map which has been built by thousands of people. It uses a wiki-like approach to mapping – anybody can edit and re-use the content. Because it’s all open data, you can use it however you want in your own learning, work, and leisure.<\/p>\n

There is a huge amount of Welsh-language data in OpenStreetMap.<\/p>\n

It’s independent of proprietary mapping providers, allowing you freedom to work with the data in your own projects.<\/p>\n

The underlying code is also freedom-respecting software and open source. As the Mapio Cymru project we have built a showcase map<\/a> which shows Welsh-language names for features including places, roads, rivers, and so on.<\/p>\n

How to run an Overpass query<\/h2>\n

The quickest way to try Overpass queries is to visit the Overpass Turbo website<\/a>.<\/p>\n

The screen will be divided into an editor panel and a map\/data viewer panel. Now do this:<\/p>\n

    \n
  1. Write (or paste!) a query into the editor.<\/li>\n
  2. Click the Run button.<\/li>\n
  3. The results are shown in the data viewer.<\/li>\n
  4. Within the data viewer you can select Map tab or the Data tab.<\/li>\n<\/ol>\n

    You’ll be following these same steps every time you run a query.<\/p>\n

    Towns query<\/h2>\n

    Here is a simple query you can use. First drag the map and zoom until it shows an area you want to investigate, e.g. a part of Wales. Then follow the above steps using this query.<\/p>\n

    node[\"place\"=\"town\"]({{bbox}});\r\nout;<\/pre>\n
    Bingo, you should now see towns plotted on the map area you’ve selected. Congratulations on accomplishing your first Overpass query!<\/p>\n
    The data<\/h2>\n
    Select the Data tab in the data viewer to see the data. It will be in the default format, which is XML.<\/p>\n
    Here’s a portion of the XML data you’ll see for the results of the above query, for two towns:<\/p>\n
    <node id=\"8997358\" lat=\"51.5912466\" lon=\"-2.7517629\">\r\n  <tag k=\"name\" v=\"Caldicot\"\/>\r\n  <tag k=\"name:cy\" v=\"Cil-y-coed\"\/>\r\n  <tag k=\"place\" v=\"town\"\/>\r\n  <tag k=\"population\" v=\"11200\"\/>\r\n  <tag k=\"postal_code\" v=\"NP26 4\"\/>\r\n  <tag k=\"wikidata\" v=\"Q722585\"\/>\r\n  <tag k=\"wikipedia\" v=\"en:Caldicot, Monmouthshire\"\/>\r\n<\/node>\r\n\r\n<node id=\"21413062\" lat=\"51.8591257\" lon=\"-4.3115907\">\r\n  <tag k=\"is_in\" v=\"Wales\"\/>\r\n  <tag k=\"name\" v=\"Carmarthen\"\/>\r\n  <tag k=\"name:br\" v=\"Caerfyrddin\"\/>\r\n  <tag k=\"name:cy\" v=\"Caerfyrddin\"\/>\r\n  <tag k=\"name:en\" v=\"Carmarthen\"\/>\r\n  <tag k=\"name:ja\" v=\"\u30ab\u30fc\u30de\u30fc\u30bc\u30f3\"\/>\r\n  <tag k=\"name:la\" v=\"Moridunum\"\/>\r\n  <tag k=\"name:ru\" v=\"\u041a\u0430\u0440\u043c\u0430\u0440\u0442\u0435\u043d\"\/>\r\n  <tag k=\"place\" v=\"town\"\/>\r\n  <tag k=\"population\" v=\"14185\"\/>\r\n  <tag k=\"population:date\" v=\"2011\"\/>\r\n  <tag k=\"source\" v=\"NPE\"\/>\r\n  <tag k=\"source:population\" v=\"Census\"\/>\r\n  <tag k=\"wikidata\" v=\"Q835835\"\/>\r\n<\/node>\r\n<\/pre>\n
    As you can see, the name:cy tag has the town’s name in Welsh. There are equivalent tags for other languages. There’s also a tag called name without a language code, here’s the definition of the name key<\/a>.<\/p>\n
    In general name:cy will provide the name in Welsh for anything on the map – if it’s been submitted.<\/p>\n
    The other data in the examples above should be fairly self-explanatory, and include latitude and longitude, Wikidata item identifier, and other things.<\/p>\n
    Note that OpenStreetMap is always a work in progress. You’ll see pretty good data for many queries although some others will display gaps. (You can edit\/add place names on the map, and other features and their tags.)<\/p>\n
    Change your Overpass Turbo map to Mapio Cymru<\/h2>\n
    \"\"<\/p>\n
    Within Overpass Turbo your underlying map will probably be the main OpenStreetMap. This is OK but it won’t always display all names in Welsh.<\/p>\n
    You can change it to the Mapio Cymru map server, like this:<\/p>\n
      \n
    1. Select Settings menu<\/li>\n
    2. Select Map<\/li>\n
    3. In the Tile-Server box put: \/\/openstreetmap.cymru\/osm_tiles\/{z}\/{x}\/{y}.png<\/strong><\/li>\n<\/ol>\n
      Please note that when you click on map pins any links will still go to the main OpenStreetMap.<\/p>\n
      Farms, cities, and other places<\/h2>\n
      You can take the query above and modify it:<\/p>\n
      node[\"place\"=\"farm\"]({{bbox}});\r\nout;<\/pre>\n
      Spot the difference between this query and the one above. Alternatively use one of the possible key values for place<\/a>. For example you can use “village”, “city”, “island” and so on.<\/p>\n
      Your bounding box<\/h2>\n
      In general:<\/p>\n