[Talk-us] New I.D Feature

Steven Johnson sejohnson8 at gmail.com
Wed Nov 12 21:33:47 UTC 2014

I share Sarah's skepticism about importing ZCTAs. ZCTAs are generalized
polygons created by the US Census Bureau and derived from *point* data
furnished by the US Postal Service. Given the variability of ZIP codes in
general, and the fact that OSM is two steps removed from the source data
makes ZCTAs problematic.

Likewise, postal cities are a fiction of the US Postal Service and in many
localities, bear little relation to the actual, legally recognized
administrative boundaries. Similarly, CDPs serve as a place name for named
places that typically have no boundary, e.g. Tysons Corner in suburban
Washington, DC. I can see CDPs imported into OSM before postal cities. The
CDPs have a regular and well-understood update cycle and a centroid. The
same cannot be said of postal cities and I think that trying to map ZIP to
city on a one-to-one basis is fraught with difficulty all the way round.

Sort of related to this: I gave a presentation at SotM-US in Portland where
I tried (with very modest success) to argue that our addr:* tagging scheme
is overloaded, making it difficult to search for the 'Stone Brook Drives',
to disambiguate directional prefixes/suffixes, and so on. Might be
worth talking about the general addressing scheme in the larger context of

-- SEJ
-- twitter: @geomantic
-- skype: sejohnson8

There are two types of people in the world. Those that can extrapolate from
incomplete data.

On Wed, Nov 12, 2014 at 4:16 PM, Clifford Snow <clifford at snowandsnow.us>

> On Wed, Nov 12, 2014 at 1:10 PM, Sarah Hoffmann <lonvia at denofr.de> wrote:
>> If I understand you right then the 'secondary cities' are
>> the actual cities/towns/villages already mapped as either
>> place nodes or administrative boundaries. Those are already
>> used by Nominatim.
>> So it seems the primary cities are what I was thinking of when
>> referring to postal cities and they can actually be inferred
>> from the postcode. If that is right, it should be somehow
>> possible to add that concept to Nominatim. I'd have to give
>> it a bit of thought.
> I think that might solve a problem with Census Designated Place, CDP. If
> the CDP has a different name than the postcode city, Nominatim might have a
> problem today.
> Clifford
> --
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