I just signed up because I noticed that OpenStreetMap thinks that Brookline, MA is in Suffolk County, but it's actually in Norfolk County. It's not clear to me - do I have the ability to personally edit this information, like Wikipedia? Or do I have to file a ticket?

asked 10 Jul '17, 07:00

robatino's gravatar image

accept rate: 0%

edited 10 Jul '17, 07:04

This is not something you can edit by just changing a simple text from "is in this county" to "is in other county". OpenStreetMap (or more precisely, the OpenStreetMap geocoder, Nominatim) deduces the information from the county boundaries. Here are what OpenStreetMap believes to be the county boundaries for Suffolk


and Norfolk


As you can see (at least at the time of writing this), the city of Brookline is clearly in Suffolk County according to these boundaries. If Brookline is in Norfolk, as you say, then both these boundaries are wrong and need to be changed. This is something that everyone can do (from a "having the permission to do it" point of view), but for a new signup editing boundaries can be a daunting task since they are often not drawn as stand-alone geometries, but re-use roads or rivers to form the boundary, and if you are not careful you can break other parts of the map by changing a geometry.

Perhaps you could point us to a source from which we could derive the correct boundaries and then an experienced mapper could look at the problem?

permanent link

answered 10 Jul '17, 07:38

Frederik%20Ramm's gravatar image

Frederik Ramm ♦
accept rate: 24%

edited 10 Jul '17, 07:39

Thank you for the detailed information. I live in Brookline, so I know for a fact that it's located in Norfolk County. I don't know if it's possible for parts of a city or town to be in different counties, but I'm pretty sure that Brookline is entirely contained in Norfolk County. When you refer to "correct boundaries", are you referring to Brookline, to Norfolk County, or both? (Unfortunately I probably can't provide the information for either of those, but someone who knows how to use the information should also know where to find it.) The following link indicates that Brookline, MA is noncontiguous with the rest of Norfolk County (which I didn't realize) which is probably why it's broken.


And this map illustrates it:


(10 Jul '17, 07:56) robatino

Yes it seems as if the ex-clave covering Brookline is missing. I would suggest taking this up on the talk-us list, there is a current interest in US sub-state boundaries and you will be sure to find somebody there willing to help. See https://lists.openstreetmap.org/listinfo/talk-us

(10 Jul '17, 08:01) SimonPoole ♦

It was ok in late 2014: http://overpass-turbo.eu/s/qib - it got broken in this edit http://www.openstreetmap.org/changeset/25407313 and then wrongly "repaired" in this http://www.openstreetmap.org/changeset/25426805

(10 Jul '17, 08:05) Frederik Ramm ♦

I posted https://lists.openstreetmap.org/pipermail/talk-us/2017-July/017529.html , and got a reply saying it's fixed in https://www.openstreetmap.org/changeset/50175342 . The above links http://www.openstreetmap.org/relation/2298154 and http://www.openstreetmap.org/relation/1840539 appear to be correct now, though a search for "Brookline, MA" on OpenStreetMap.org still says "Suffolk County". How long does the fix take to propagate?

(10 Jul '17, 13:37) robatino

Depends on the data consumer. Any time from a few minutes to a few weeks.

Basically what happens is that each consumer (map renderer, geocoder, router, etc.) project refreshes their copy of the database of the main one at intervals they have picked and it won't show up on their product until they have updated their internal database with the changes from OSM.

Nominatim, the software/project giving you the county Brookline is in, despite being linked to by OpenStreetMap reference map page is actually a separate project. I believe their update is fairly quick so you should see the fix there in a day or so.

(10 Jul '17, 14:23) stf

To answer my own question above about whether it's possible for a city or town to be in different counties, the answer is yes - a list is at https://en.wikipedia.org/wiki/List_of_U.S._municipalities_in_multiple_counties . If I search for one of them at Nominatum, it only returns one county, though, so it doesn't appear to be possible to associate more than one.

(10 Jul '17, 14:42) robatino

@robatino I believe this is because no single point belongs to more than one county (that is, county borders do not overlap). I don't know what Nominatim does to associate an area to a given county, it depends on the Centre Point I believe (I choose Joliet, Illinois, from that wiki list: https://www.openstreetmap.org/relation/124820 linked to Will County http://nominatim.openstreetmap.org/details.php?place_id=172756881) but a simple reverse geocoding works fine. If you click on "where I am" at this point: http://bit.ly/2sRfutv you get "Joliet, Kendall County" while crossing the border here: http://bit.ly/2uS77z4 it becomes "Joliet, Will County". Same city, but different county, as we expect.

(12 Jul '17, 20:20) Alecs01
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question asked: 10 Jul '17, 07:00

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last updated: 12 Jul '17, 20:20

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