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    Search and retrieve bounding boxes and shapes

    So we have a cool project running called Chalice, text-mining and locating historic placenames to build a historic gazetteer stretching back beyond Domesday, for a few areas of England and Wales. Claire Grover from LTG had some questions about using a shape based rather than point based gazetteer during “geographic information retrieval”, I thought it worth posting the answers here, as Unlock Places is able to do a lot more in public since the addition of Ordnance Survey Open Data.

    http://unlock.edina.ac.uk/features/Edinburgh – now by default returns info from OS Open Data sources including Boundary-Line as well as Meridian2 which have bounding boxes and detailed shapes for things like counties, parishes, though note they are all contemporary.

    (The above is just an alias for
    http://unlock.edina.ac.uk/ws/nameSearch?name=Edinburgh )

    So that’s a way to get bounding boxes and shapes for places that are in geonames, by comparing with other sources. The default search results have bounding boxes attached, one must look up a link to see the detailed geometry.

    Here’s how then to filter the query for place-names to a specific bounding box:

    We have ‘search for names inside the shape which has this ID’ on our todo list but don’t yet have a pressing use case – for many things bounding boxes are enough, one even wants that bit of extra inclusion (e.g. Shropshire’s bounding box will contain a lot more than Shropshire, but as Shropshire’s boundary has changed over time, some approximation about the shape is actually helpful for historic geocoding).

    Note that all place-names for UK will have county containment information – we added this for Digimap – one day they may start using it!

    You may also be interested to play around with http://mapit.mysociety.org/ – it has all the same OS Open Data sources and mostly the same set of queries but in places does a little more – it doesnt have geonames integrated, though.

    Lasma did some work on conflating different mentions of places based on point-polygon relationships (e.g. if a shape and a point have the same name, and the shape contains the point, the name is “the same thing”). However this was an experiment that is not really finished. For example –
    http://unlock.edina.ac.uk/ws/uniqueNameSearch?name=Edinburgh – i see this returns a shape in preference to a point – and wonder if it always will, if a shape is available. However this is not much use when you actively want a set of duplicate names, as you do while geoparsing. It would be good to revisit this, again, with concrete use cases. And of course it would be good to do this for much wider than the UK, with shapes extracted from OpenStreetmap. Investigating…

    3 responses to “Search and retrieve bounding boxes and shapes”

    1. […] will help improve the quantity of samenesses that we can establish, is filtering searches to be limited by counties – either detailed boundaries or bounding boxe… that will definitely contain the county. Contemporary data is now there for free re-use through […]

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