[Talk-us] An admin_level for CDPs?

stevea steveaOSM at softworkers.com
Mon Dec 31 20:30:35 GMT 2012

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 
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.


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