[Talk-us] New I.D Feature

Richard Welty rwelty at averillpark.net
Sun Nov 9 15:33:58 UTC 2014

On 11/8/14 3:11 PM, Sarah Hoffmann wrote:
> Postal towns is really a concept that wasn't taken into account when 
> the Karlsruhe address schema was developped and IMHO doesn't really 
> fit. I'd really like to see some discussion in the US community about 
> how it can be tagged including considering the possibility to come up 
> with a brand new way of tagging it. If you then come to the conclusion 
> that addr:city is still the best way to go, so be it. But I'd be far 
> more happy to support something in Nominatim that fits exactly the US 
> situation than hack some European tagging system until it hopefully 
> gives the right result most of the time. Kind regards Sarah (your 
> friendly nominatim maintainer)
ok, here are some things to think about:

1) the Census Bureau has an area based version of zip codes
(postal codes to the non-US types) called ZCTA. it is not a
complete representation, it covers about 30,000 of the
50,000 unique zip codes, but it covers all the ones that
can be reasonably envisioned as areas.

2) missing from ZCTA is the mapping from zip codes to
"postal city" as you call it. there is more to it than just a
many-to-one mapping, which i'll address in a minute.

3) most of the US mappers are opposed to importing this
into OSM for a couple of good reasons, i'm one of those

4) however, there is also a movement in the US mapping
community towards having certain types of data kept out
of the core OSM database, including various types of
admin boundaries. there are two projects looking at
admin boundaries in this manner; i'm working on one of

5) so if we could 1) come up with the ZCTA->City mappings
and 2) provide them in a convenient external database for
use by geocoders, is this something that might reasonably
be made use of in Nominatim?

i've been considering what a project to crowdsource
the zip->city mappings for the US might look like. currently
the data exists in OSM to handle about 4% of the mappings,
but a maproulette style challenge might get us a lot of
the rest.

as for that many to one mapping that isn't, basically,
for each zip code there is a primary city and potentially
a number of secondary cities. the primary city is the
city name of the post office that serves the routes; the
secondary cities are generally traditional place names
within the delivery area; for example, for years i lived
in the Lansingburgh neighborhood of Troy NY, and
the post office would deliver mail for either city name.
any effort to crowd source this data would need to take
care of that detail.


rwelty at averillpark.net
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