I have been pondering the use of the admin_level
key in the USA, and have come to the realization
that while values 2, 4, 6 and 8 are correct for
national, state, county and city boundaries
(respectively), it is more complicated than that.
It is likely time to end the pretending this
oversimplification is sufficient. It is not.
A useful tool is
http://www.itoworld.com/map/2#fullscreen which
shows admin_level boundaries from 2 to 11 (11 for
Germany and Netherlands only) in different
colors. Yes, it is true in the USA that for
those boundaries which are tagged correctly (all
50 states, many or even most counties, some
cities) we do see good boundaries and colors.
However, there are boundary polygons in OSM which
are an odd duck in the USA: a notable one is
Census Designated Places (CDPs), which came from
the TIGER import. These are a bit like cities in
that they are often a similar size and population
of a town or rather small city. But they are not
strictly cities, in that they are derived from
the federal government (not "negotiated" with a
state government like a city which is or has
incorporated) crafting them for statistical
purposes. CDPs have no legal basis as
incorporated cities do. In fact, many of the
residents of these areas may not even be aware of
the boundaries of their own CDP. However, CDPs
are useful, as they often give name and shape to
a place or area which otherwise might not have
one, and frequently the CDP yields the only
boundaries for doing so.
In other words, CDPs (and others, see below)
really are administrative divisions in the USA,
we just don't often think of them that way, and
so we don't (often) classify them into a
hierarchy. I do believe it is proper and useful
to do so, but of course we should strive to get
to as correct as a consensus/result as we can.
I have edited
http://wiki.openstreetmap.org/wiki/United_States_admin_level
to reflect the reality of this more complicated
picture in the USA, some states which don't
cleanly follow the 2/4/6/8 model, and at least
some of these "more federal" entities. (There
are also LAFCos in California, as well as COGs in
many states, which are state-defined, in addition
to MPOs, which straddle a local/federal level,
and PSAs, CSAs, MSAs, and µSAs, defined by the
executive branch of the federal government).
As a starting point, we can keep this discussion
simple and decide whether a CDP might rightly be
assigned an admin_level of 5, as it is both a
federal and quasi-local entity which correctly
"lands in the middle" (below state but above
county), or whether it might actually be lower
than a city (but implying subordinate to? --
doesn't seem correct...) with an admin_level of 9.
SteveA
California
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