Q: Can I map the geographical center, northenmost point, etc. of a country, state, region? They are even mentioned on Wikipedia, and proven in a PhD thesis.

A: Of course you can't, unless there is at least a pile of stones there...

I'm sure it is a bad practice but I can't find the exact phrase to discourage people...

asked 05 Jan, 19:27

jidanni's gravatar image

accept rate: 0%

edited 05 Jan, 19:29

I guess you could, but OSM is basically a geographical database and there is a fairly standard set of tools for using the data contained in it. For example, Posgresql with Postgis extensions are often used for display or analysis. And using those it is easy to query for the centroid of an area. So there is no particular reason to map the centroid. Unless, as noted in the wiki, there is actually something there of interest to be mapped.

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answered 05 Jan, 22:00

stf's gravatar image

accept rate: 19%

Well "no particular reason to map" is good, but I am looking for a "particular rule" , "not to map", else people will map the center of (insert favorite country here), without there needing to even be a single wood stake there. (Unless, yes backed up by the facts, that is OK.) (My interpretation of the wikis is that is not OK, fact or not. But I wish the wiki would be super clear.)

(06 Jan, 01:51) jidanni

The briefest explanation might be in the statistical properties part of the Verifiability page. Verifying the entirety of a boundary used to calculate a centroid would usually fall into the same problems.

This would also be redundant data as it is entirely calculated from an existing boundary and has an additional maintainability problem as any change to the boundary would not be automatically propagated to the centroid node and the note could easily be moved accidentally by another mapper leaving it not just redundant but incorrect.

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answered 05 Jan, 23:11

InsertUser's gravatar image

accept rate: 19%

All I know, is except for political and e.g., national park boundaries, all other points and lines need at least some pile of rocks before one can place a point on the map. I just can't find the best clause in the wiki...

(06 Jan, 01:40) jidanni

And then some folks say "Well you can't see the Nurdsburg County border on the ground, but you still can map it. That gives me the right to map lots of other stuff that needs no ground proof." I wish the wiki would be clearer.

(06 Jan, 01:42) jidanni

And also even if the United Nations Committee of Geographical Wizards unanimously declared an exact X,Y to be the center of Greenland. All there is there is just ice. So I need a clause in the wiki to keep people from placing a point there. Or an explicit clause in the wiki encouraging it.

(06 Jan, 01:44) jidanni

OK, never mind about centers, magnetic poles, axis poles, and other things that change. Let's say the United Nations Committee of ... said some exact X,Y is where whatever non-changing thing is... but if you go there there is nothing on the ground... so the wiki should say in what cases adding a point is welcomed vs. not.

(06 Jan, 01:48) jidanni

Openstreetmap data should be based on real features that can be determined to be true or false by ordinary local mappers who have in interest in that type of feature. Something like the calculated center of an area is metadata, calculated from the real boundaries of an area, and should not be mapped in Openstreetmap.

However, sometimes placing a node near the center of a large, imprecise area (like a sea or large bay or a continent) is the best way to represent a large, diffuse feature in Openstreetmap - that's different than adding a calculated center point to a feature which has a verifiable boundary, like an island or a country with defined borders.

(06 Jan, 02:44) Joseph E
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question asked: 05 Jan, 19:27

question was seen: 174 times

last updated: 07 Jan, 18:18

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