I have some code that works out which UK county a place node falls in. This is failing for some coastal towns / villages, because the latitude and longitude defined for the place node is actually in the sea or on the beach, and therefore falls outside of the county boundary.

An example is Hugh Town in the Scilly Isles. Here's how it looks on Google Maps, which doesn't show the beach.

Is this intentional, or could the node positions for such places be adjusted so that they were on land? I could easily come up with a list of them.

asked 06 Aug '12, 09:26

Dave's gravatar image

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It is best to map town and village areas as polygons so that the nominatim works properly, addresses get linked to nearest node otherwise. This will put the name in the middle of the polygon on the map page. I do not know if your code also searches for village and town polygons as well as nodes. Some say after drawing the polygon the node is not needed any more so delete it, again to assit the nominatim. I hope this is not a problem for your purposes.

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answered 07 Aug '12, 13:55

andy%20mackey's gravatar image

andy mackey
accept rate: 4%

edited 07 Aug '12, 14:03


Thanks Andy, that's very useful information. At the moment my code doesn't look for village/town polygons. I will add that, and probably geometrically generate my own centre points for them (as my code needs to calculate proximity to points of reference, rather than positioning within polygons).

(07 Aug '12, 14:39) Dave

Hi Andy. It is my understanding/interpretation that it is normally best to use nodes for places (https://wiki.openstreetmap.org/wiki/Key:place) (towns, villages, etc) and areas for administrative boundaries (https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative). See also this discussion: (http://help.openstreetmap.org/questions/4658/tagging-areas-as-place-vs-boundaryadministrative).

(08 Aug '12, 00:04) pbb

Peter I looked at your links thanks,but one seemed to be empty. The decision to use nodes or polygons seems to be split. In my experience if I search for a street I have found that it will grab the nearest town or village which may not be the correct one. Nodes may work if all houses,and buildings have all the address tags filled in.Back to Dave's Question I wanted to add relevant info for him or others doing similar work. I'm no expert!

(08 Aug '12, 09:10) andy mackey

Your code should definitely prefer positioning withing polygon if it exists. The other calculation (distance on place node, real or virtual) will lead to many errors. Imagine two adjacent villages, one is 10x10 km square, one is 1x1 km square. If you use the geometrical polygon centre, a street within the big village but nearby the smaller village will be identified to the wrong village. If you use the real "place" node, you have to rely on its positioning by contributors (fluctuating).

(08 Aug '12, 12:23) Pieren

Note that it is possible to link the place node and the boundary with the relation role "admin_centre" (although we have cases where one boundary includes many places, usually only one of them is the administrative centre).

(08 Aug '12, 12:25) Pieren
showing 5 of 6 show 1 more comments

In my opinion, place nodes should be put at the position that is locally considered to be the "center" of the locality, not some mathematically determined point.

Judging by the Hugh Town map, I would have put the place node where Lower Strand, Church Street, Silver Street, Garrison Lane and Hugh Street meet.

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answered 07 Aug '12, 08:21

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Thanks pbb. I've now made my first edit, and done precisely that ;-)

(07 Aug '12, 15:59) Dave

Sure you can move the node towards the inner country. Actually the best way is, to put the node in the center of the area, where it belongs to.

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answered 06 Aug '12, 11:45

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question asked: 06 Aug '12, 09:26

question was seen: 2,803 times

last updated: 09 Aug '12, 17:03

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