Recently there have been changes in the provinces in Norway. I would like to know how I can find the old provinces in OSM. How do I search for those?

asked 18 Mar '20, 13:57

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Mischa
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Your question is not really clear: are you looking for the current boundaries for the provinces so that you can update them, or are you looking for the previous versions because the updates have already been done?

(18 Mar '20, 19:47) SimonPoole ♦

Or a third alternate: are you looking for a current relaiton that defines the old boundaries?

(18 Mar '20, 19:50) InsertUser

Hi,

I'm sorry if I wasn't clear. What I mean is, how do I find the old relation that defines the former boundaries. Example: per January 1, 2020 the provinces of Buskerud, Akershus and Østfold were merged into a new province, Viken. How do I find the relation that defined the former province Akershus? What happens to those relations? Are they deleted?

(19 Mar '20, 06:42) Mischa

OK, unluckily the answer is "it depends".

The good news is that nothing in OSM is actually ever "deleted" so in principle the old information will still be there in any case. However, the bad news, it may be a significant amount of work to extract whatever information you want to have.

To the "it depends" bit: what happens with the old relations and old border ways is a question of local policy/whatever the person making the changes decided to do. You can and should naturally should ask on the NO communications channels about this. In my experience (this year was the first time after many years that I didn't organize the similar effort in Switzerland to update our municipality boundaries), this tends to be a matter of much debate.

But we don't have to wait for that to have a look. The changeset that made the new county "Viken" "active" was https://www.openstreetmap.org/changeset/78911743#map=5/65.440/17.930 (found by working backwards from the current data).

It says in its comments that the old boundaries were retained as multipolygons, and see for example https://www.openstreetmap.org/relation/406106 for Akershus.

PS: I'm not particularly enthusiastic about retaining the old boundaries as unspecific multi-polygons, as they cannot be searched for and found that way, but still add complexity to our data.

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answered 19 Mar '20, 09:39

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SimonPoole ♦
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edited 19 Mar '20, 09:42

Thanx! That is already much clearer. But what I don't quite understand is that working backwards. If I work backwards from the new county Viken I get a different changeset. From which relation did you work backwards?

(19 Mar '20, 13:27) Mischa

If you work backwards through https://www.openstreetmap.org/relation/10155539/history , the changeset Simon mentioned is the earliest one with the tag boundary=administrative. The relation existed prior to that, as it was created earlier in preparation for the changes. But it was tagged as proposed:boundary=administrative, which would be ignored by most users of the data. As it happens the old Akershus relation has been treated in a similar way in reverse, as it is now tagged was:boundary=administrative. (As Simon says there are multiple approaches to this, so nobody reading this should count on this working beyond this specific case).

(19 Mar '20, 16:12) alan_gr

If it helps to visualise it, you can also look at http://osm.mapki.com/history/relation.php?id=10155539 .

(19 Mar '20, 16:19) SomeoneElse ♦
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question asked: 18 Mar '20, 13:57

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last updated: 19 Mar '20, 16:19

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