Posted by munro 20 hours ago
"A full postcode identifies a group of addresses (typically around ten) or a major delivery point."
https://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdo...
Also postcode data is licensed by the Royal Mail, not free.
https://docs.os.uk/osngd/data-structure/administrative-and-s...
Not sure under what basis you think they are "supposed" to be a certain way but postal codes originated as a signifiers of areas, even in the UK.
US postal codes absolutely have overlap in area, because they do not divide land, they direct delivery routing.
https://web.archive.org/web/20030119031055/http://users.rcn....
My point is that postal codes aren't "supposed" to work any particular way. They work in what ever way they are specified to work at any particular point in time in any particular place.
Zip codes in the US are related to delivery routes. Prior postal codes in the US were not. UK post codes are currently hyperspecific to a single location. Previously they were not.
It'd find it difficult to believe that when the system was originally created, mail delivered by a Nevada post office to a physical location in California had a zip code starting with a 9 rather than an 8.
My grandfather's postal code growing up in the US was simply "6". He did not have a zip code, because they had not been invented yet.
We didn't quite get enough info to determine the particular route until Zip+4 in 1983.
> It'd find it difficult to believe that when the system was originally created, mail delivered by a Nevada post office to a physical location in California had a zip code starting with a 9 rather than an 8.
When the US first implemented postal codes, 100+ cities had a duplicate postal code of "1", which was the first postal zone within that particular city. We've increased the specificity of our postal codes twice since then. (well, three times if you count IMb)
But more to your modern zip code example -- addresses and their 5 digit ZIP codes historically followed the post office together in lock step. (This is why many system have separate "mailing addresses" from "physical addresses", they weren't always the same thing) -- e.g. if you lived in rural town and your mail was delivered from a different town you'd have something like a rural route address and both the municipality and the zip code you'd put on the letter would be for town the post office was in, not the town you lived in.
For example, when I was young and wrote a letter to my grandmother, I wouldn't put her street address on it... because she didn't have one. I'd address it to her rural route number and box number, and I would address it not to the town she lived in, but to the town the post office was in, and the zip code of that post office.
In the case where this was across state lines, your mailing address would be a different state than where you lived.
This is part of the reason why USPS has been converting from RR addresses to the Locatable Address Conversion System. Because it was difficult for first-responders to find homes when people calling didn't have addresses that matched where they actually were.
When I had to work with addresses in other countries, I found out that is not that normal.
The United States can be more granular, as a "full postcode" equivalent in the United States is ZIP+4, which can resolve down to an individual building, mailbox, or person, depending on the characteristics of the location.
Very complex problem globally, but the consequences can be high if you sell the wrong number type to a customer in the wrong location (and sometimes the EU and its member states can have precisely opposite legal requirements).
The US is relatively simple, with rate centers, but in some countries you actually have to draw geojson boundaries and find out exactly which location the company's headquarters resides within, down to the meter. If your boundaries aren't precise enough, you can get into trouble.
It's been about a decade since I was involved in that, so I'm curious if it's easier these days. There's not, however, a lot of incentive to fix it, as in many countries a few telco providers control everything.
I believe the demand for this was to visualize attributes on a map by coloring polygons, and the dataset was addresses that already had zip codes.
(Please stop coloring polygons by attribute: it gives false impressions because areas are unequal. Instead, use a scale of dot density. Or marker size, which has its own perceptual issues.)
However misguided, coloring zip code polygons gives you things like maps of customer data. But you could just as well geocode each address and assign it to a county or other boundary. (news flash: the geocoding database is derived from the same line data as the ZIP code project.)
Some zip codes represent a single building. Example 20500 is the White House. The Pentagon is so big it has several zip codes.
https://convene.com/catalyst/office/buildings-new-york-city-...
It used to be that the first 3 digits of a zip code sent that mail to the "main" post office building (the one that has loading docks for like 10-30 tractor trailers on one side of the building). Even if you were mailing a letter to the same zip, it went to that building to be sorted and returned to the local office before delivery. Nowadays, everything goes to central facilities where stuff is scanned and sorted. In Kentucky, almost all mail goes through Louisville.
The "city" on my address growing up was a CDP[1], and it is now a city that I live 2 miles from rather than the one that I live less than a mile from.
And in no instances have I ever run across use cases where these are worth paying any substantial money for. If USPS is going to jump into the fray here, really bad look (and probably net negative revenue for them) to offer as a paid product.
Whatever you're grouping is likely better served by some grouping based on geography, not based on delivery routes. You probably wouldn't group by telephone company central office either, unless you're telco related.
We want to group by geography, zip codes are easy and vaguely geographic, lets use that is kind of a valid decision, but it's deeply frustrating :p
In fact, these were invented by Nielsen, and they determined them just by measuring which city's TV stations are predominantly watched in each county, and assigning each county to one DMA based on that.
The ATMs never got mail.
We use https://github.com/OpenDataDE/State-zip-code-GeoJSON - it's from 2010, but open it in Claude and use the free-to-download data source to regen from the most recent census.
Ireland was the last country in the OECD to create a postcode system. In July 2015 all 2.2 million residential and business addresses in Ireland received a letter notifying them of the new Eircode for their address.[4] Unlike other countries, where postcodes define clusters or groups of addresses, an Eircode identifies an individual address and shows exactly where it is located. The system was criticised...[5]
...for using an unsequenced code limited to postal addresses...[67][68]Blog post: https://austinhenley.com/blog/coord2state.html
HN discussion: https://news.ycombinator.com/item?id=44175356