I don't think I have encountered a situation where an administrative boundary
at the city level of higher follows a road (i.e. if the road changes alignment,
the boundary changes alignment). Sometimes boundaries below the city level are
defined by roads, but those are not legally defined boundaries. There
occasionally are legal boundaries defined on a river, but only if the river
changes course gradually and naturally. If there is a radical (e.g. a
post-flood cutoff of an ox-bow) or man-made (e.g. a dam causes flooding that
shifts the midline), the boundary stays fixed at its original boundary.
So, while boundaries might regularly fall on right of way or centerlines of
roads and rivers, they are rarely fixed to those lines (which takes away some
of the future benefit of using a highway in an admin boundary relation).
Brett Lord-Castillo
Information Systems Designer/GIS Programmer
St. Louis County Police
Office of Emergency Management
14847 Ladue Bluffs Crossing Drive
Chesterfield, MO 63017
Office: 314-628-5400
Fax: 314-628-5508
Direct: 314-628-5407
-----Original Message-----
Date: Mon, 31 May 2010 16:02:15 -0400
From: Richard Weait <rich...@weait.com>
Subject: Re: [Talk-us] Admin limits
To: "talk-us@openstreetmap.org Openstreetmap"
<talk-us@openstreetmap.org>
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<aanlktinwgqk7knoendqyifj6mjmite1kqix77pa5h...@mail.gmail.com>
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On Mon, May 31, 2010 at 3:49 PM, Richard Welty <rwe...@averillpark.net> wrote:
> On 5/31/10 11:06 AM, Nakor wrote:
>> ? ? Hello,
>>
>> I just have a quick question on admin limits. I have seen various
>> practices when they are overlapping another feature (road, river, ...)
>> and I was wondering if there was a consensus on the way to do it as well
>> as the pros and cons of each methods.
>>
>> * Two separate ways with separate nodes
>> * Two separate ways with common nodes
>> * One way holding both tags (e.g. highway=residentail and admin_level=8)
>> * other?
>>
> most think it should be your first choice, two ways with separate nodes.
> some argue for
> choice 2 (generally GIS people who don't ?like duplicate nodes), and
> some bots and other
> tools push that way.
>
> i've not heard of anyone advocating choice 3. me, i stick with 1, if it
> were ever decided
> that 2 was the thing to do, it'd be possible to get there with a bot.
You will also hear folks suggest tag the highway as it exists, then
add the highway to a boundary relation for the admin_level.
When applied correctly, this makes corrections to the road geometry
simple, makes the boundary follow the corrected road without a hassle,
and is an excellent use of a relation. This is not an argument to put
the boundary on the road if the boundary does not belong on the road.
The same benefits would apply for a boundary that follows a river or
other exiting feature.
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