[OSM-talk] open question about boundaries sharing nodes with ways or nodes

[Colin Smale]

How is the boundary legally defined? If it is a set of coordinates or a
line on a map, then there is no intrinsic link with the line of the
highway. If the highway is realigned, this will not (automatically)
affect the boundary. This may have already happened in the past, so the
lines are "almost" colinear but not quite. 

However, if the boundary is legally defined in a more descriptive
manner, such as "following the centre line of highway X" then there is a
real link between the line of the highway and the line of the boundary,
and one cannot be changed without changing the other. 

Where boundaries appear to follow a highway, they are not always aligned
to the centre line. This can give headaches for road maintenance, police
jurisdiction etc. The boundary may be following the edge of the
carriageway, or a hedge/ditch a couple of metres away, so the whole road
is actually in one administrative area. 

So all in all, I would suggest it would be better to not share ways, and
not share nodes either - unless you are very sure that the boundary and
the highway are legally linked together. 

--colin 

On 2015-10-14 09:49, Badita Florin wrote: 

> It is interesting the things that you discover when trying to do the import of a whole county, in this case, Mexico 
> 
> Our task is to delete all the existing admin_level=6 boundaries and start fresh, but this seems much more things needs to happen before you do this.  
> 
> There are over 500 nodes or ways that share a common node or follow the same path with the old boundaries that we want to remove, so we can add the new boundaries. One interesting topic had have sprung up is this, what are the procedures for dealing with boundaries that run along a road, waterway. 
> 
> A query that we had build to detect this kind of shared nodes and ways looks like this http://overpass-turbo.eu/s/bZA 
> 
> You can adapt the script and share your results, to see if there are other examples that can be included here 
> 
> Now it has come up a question, what happens for example with cases like this. 
> 
> A way that is two things simultaneously, for example a highway and a boundary at the same time. There are some cases like these in the state of Michoacan and I can't just de-glue the bad nodes because the way  itself seems to be two things at the same time.  This is the issue in question, your query identified the following two nodes: 
> 
> Nodes 1856092007 [1] and 1856092002 [2] , which limit the following  way [3] between such nodes. This way is a highway and at the same time is part of the relation of a boundary. This seems invalid since it merges two types of features on the same way instead of keeping a logical separation between two different things. Is this a valid way? What if the highway is modified ? since the highway is not a legal boundary and just happens to overlap the real boundary, so if the highway  is changed for any reason, it will modify the boundary along with it. So what's the valid thing to do here? Duplicate the way to save the highway way and keep a way for the boundary separated?, I've found similar questions [4] by other users and they indicate it isn't valid but I need a more official argument because the user is upset if we remove this kind of ways from relations 
> ᐧ 
> 
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Links:
------
[1]
http://t.sidekickopen24.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XYg4XrmfHMQByL0f6nqlW3LyBkH56dL4Zf8p2wPs02?t=http%3A%2F%2Fwww.openstreetmap.org%2Fnode%2F1856092007&si=6117088740507648&pi=d9ea1099-68c4-44a7-9853-3b1c4a86d057
[2]
http://t.sidekickopen24.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XYg4XrmfHMQByL0f6nqlW3LyBkH56dL4Zf8p2wPs02?t=http%3A%2F%2Fwww.openstreetmap.org%2Fnode%2F1856092002&si=6117088740507648&pi=d9ea1099-68c4-44a7-9853-3b1c4a86d057
[3]
http://t.sidekickopen24.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XYg4XrmfHMQByL0f6nqlW3LyBkH56dL4Zf8p2wPs02?t=http%3A%2F%2Fwww.openstreetmap.org%2Fway%2F174970090&si=6117088740507648&pi=d9ea1099-68c4-44a7-9853-3b1c4a86d057
[4]
http://t.sidekickopen24.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XYg4XrmfHMQByL0f6nqlW3LyBkH56dL4Zf8p2wPs02?t=https%3A%2F%2Fhelp.openstreetmap.org%2Fquestions%2F7563%2Fwaterway-as-administrative-boundary-shared-way&si=6117088740507648&pi=d9ea1099-68c4-44a7-9853-3b1c4a86d057
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