[Talk-us] New I.D Feature

Sarah Hoffmann lonvia at denofr.de
Wed Nov 12 21:10:34 UTC 2014


On Sun, Nov 09, 2014 at 10:33:58AM -0500, Richard Welty wrote:
> 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.

Nominatim is already using a version of the ZCTA data
as an additional source. I know there are some bad errors
in there preceisly because it seems that US zip codes
don't really cover areas. The search allows a certain
degree of fuzziness by accepting all nearby zip codes but
that is really not good enough. 

> 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
> opposed.

I can see that there are good reasons not to import ZCTA.
It is just an estimate after all.

Until now I was under the impression that the postal cities
are different than postcodes in that they are well defined
areas, i.e. I thought that they are much more similar to
administrative boundaries just created by a different
branch of the government. But from your mail, it sounds
like they are much closer to the zip codes.

> 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
> them.
> 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.

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.


More information about the Talk-us mailing list