Any hints for converting from ZIP to ZIP+4 for a street address?

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Does anyone have an idea on how to find ZIP+4 codes?


a d y k e s @ p a n i x . c o m  

Don't blame me. I voted for Gore.

Re: Any hints for converting from ZIP to ZIP+4 for a street address?

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The TIGER data from the Census bureau contains a *LOT* of data.
(If only there was a good way of getting useful information out of
it.)  For each *block*, you get info like street name, range of
street numbers, Zip+4 on each side, lat/long coordinates of each
endpoint of the block, and possibly some points in the middle if
it's not straight.  It does not, however, try to give street number
ranges that are actually used (e.g.  my block is 1200-1298, which
doesn't say that the house at the end of the block is 1232 and
there's no room for 1234-1298).  The schema involves lots of big
numbers that are only unique on a per-county basis.

Assuming, for example, that you can match the street address to
a specific block (given that there may be multiple Elm Streets
in nearby towns, and possibly even in the same town, and you may have
to deal with Elm Street, Elm Road, Elm Boulevard, Elm Freeway,
Elm Lake, Elm River, and Elm Memorial Garbage Dump), you could
get the Zip+4.  Some of this might be narrowed down with the
5-digit Zip if that was known.

Warning:  as I recall, this data takes up more than one DVD and
it's heavily compressed.  Putting it in database tables would expand
it a lot.

Oh, yes, I'm also not sure about how accurate the data is or how
up-to-date it is.  Also, the data only attempts to include Zip+4
that represent *street* addresses.  Zip+4 allocated to banks of
P.O. boxes in a post office aren't included.

                    Gordon L. Burditt

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