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A ZIP+4 does not encode all information. Proof: a post office has its own zip code, for PO Boxes. The +4 is the last four digits of the post office box. If t

by bombcar 8mo ago

A ZIP+4 does not encode all information. Proof: a post office has its own zip code, for PO Boxes. The +4 is the last four digits of the post office box. If the Post Office has more than 10,000 boxes, the +4 will be duplicated.

twodave 8mo ago
Yeah, anyone who has had to work with USPS bar codes should know that internally these are called routing codes, and they come in 5, 9 and even 11 digit variants. The 11-digit one narrows down to a specific delivery point, but even that isn’t enough to derive an address (just enough to know whether you’re looking at the right one or not). Zip+4 codes also change frequently because they aren’t based on locations but on delivery routes and sequencing.
- fn-mote 8mo ago
  > Zip+4 codes also change frequently because they aren’t based on locations but on delivery routes and sequencing. This was news for me. I know the few zip+4 I memorize never change. I think the source for the parent is AI slop. See [1]. > Due to an increase in population or to the improve postal operations, the US Postal Service® will occasionally add a new ZIP Code or change ZIP Code boundaries. The plus four digits encode: > [67] : Sector or Several Blocks > [89] : Segment or One Side of a Street Note that this contradicts the parent. [1]: https://faq.usps.com/s/article/ZIP-Code-The-Basics https://faq.usps.com/s/article/ZIP-Code-The-Basics
  - twodave 8mo ago
    The census bureau (very) periodically publishes zip code data (which is where some places get their geolocation info). If you work with enough addresses you’ll find some zip+4s that are wildly far away from where they used to be. There are paid services that have better accuracy, but I’m not sure how they acquire their data.
    - bombcar 8mo ago
      Some people don't realize just how much you can "customize" deliverability with the post office, especially if you're big (like a school or large business) - you can have something that looks like your physical address, but is actually really a maildrop/PO Box at the nearby post office. You can do relatively complex forwarding that would only appear to the end users if they can decode the barcode.

by bombcar 8mo ago

twodave 8mo ago

Yeah, anyone who has had to work with USPS bar codes should know that internally these are called routing codes, and they come in 5, 9 and even 11 digit variants. The 11-digit one narrows down to a specific delivery point, but even that isn’t enough to derive an address (just enough to know whether you’re looking at the right one or not). Zip+4 codes also change frequently because they aren’t based on locations but on delivery routes and sequencing.

fn-mote 8mo ago
> Zip+4 codes also change frequently because they aren’t based on locations but on delivery routes and sequencing. This was news for me. I know the few zip+4 I memorize never change. I think the source for the parent is AI slop. See [1]. > Due to an increase in population or to the improve postal operations, the US Postal Service® will occasionally add a new ZIP Code or change ZIP Code boundaries. The plus four digits encode: > [67] : Sector or Several Blocks > [89] : Segment or One Side of a Street Note that this contradicts the parent. [1]: https://faq.usps.com/s/article/ZIP-Code-The-Basics https://faq.usps.com/s/article/ZIP-Code-The-Basics
- twodave 8mo ago
  The census bureau (very) periodically publishes zip code data (which is where some places get their geolocation info). If you work with enough addresses you’ll find some zip+4s that are wildly far away from where they used to be. There are paid services that have better accuracy, but I’m not sure how they acquire their data.
  - bombcar 8mo ago
    Some people don't realize just how much you can "customize" deliverability with the post office, especially if you're big (like a school or large business) - you can have something that looks like your physical address, but is actually really a maildrop/PO Box at the nearby post office. You can do relatively complex forwarding that would only appear to the end users if they can decode the barcode.