The ABS have an interesting factsheet on postcodes and their own 'Postal Area' interpretation (POA). https://www.abs.gov.au/websitedbs/censushome.nsf/home/factsheetspoa It starts with this statement: *"A postcode is a four digit number used by Australia Post to assist with mail delivery. Australia Post does not currently define geographic boundaries for postcodes. However, a number of organisations, such as PSMA Australia Limited, create geographic boundaries that aim to define the geographic extent of the mail delivery area for each postcode. Defining postcodes with a geographic boundary is an imprecise process, and this is demonstrated by the fact that there are variations in boundaries released by different organisations."*
Some postcodes cross state boundaries, one example is 3644 which covers Cobram in VIC and Lalalty in NSW https://auspost.com.au/postcode/lalalty https://auspost.com.au/postcode/cobram/vic/dgee https://www.google.com/maps/place/VIC+3644/ There are also regions with no postcode, eg parts of the wilderness in West Tasmania. Some postcodes cover non-contiguous areas eg 3585 which is in two parts https://www.google.com/maps/place/VIC+3585/ In VIC at least shapefiles for postcodes exist, I didn't search more broadly. The VIC data is aligned to property boundaries. https://services.land.vic.gov.au/SpatialDatamart/dataSearchViewMetadata.html?anzlicId=ANZVI0803003521&extractionProviderId=1 and https://discover.data.vic.gov.au/dataset/postcode-boundaries-polygon-vicmap-admin Google seems to have pretty accurate shapes for postcodes - but no idea of their sourcing. Regards, Adam On Thu, 17 Jun 2021 at 16:08, stevea <stevea...@softworkers.com> wrote: > I know (I know), I’m talking to the Australia list and I’m in the USA > (California). I have friends from Oz, but I’ve never been (I’d love to > visit as a tourist, it’s on my bucket list). > > In the USA, the USPS (postal service) uses five-digit “ZIP” codes (Zone, > digit 1; Improvement, digits 2 and 3; Plan, digits 4 and 5) for what you > call postcodes, the five-digit version generally identifies a single post > office, big or small. Started in the 1960s (or so), they have grown to > “ZIP+4” codes (nine digits) that seem to specify right down to a “side of a > street on a block,” single apartment building, or even individual house > level. I believe there are even 11-digit versions (crawling right up yer > bum, it seems; with 11 digits, even my cat could have his own ZIP code). > On the other hand, I have a Post Office box (identified by four digits) and > the post office is identified by its five-digit ZIP code. I once > test-mailed an envelope to myself with just nine digits properly hyphenated > (no name, no house number, no street, no city, no state), and sure enough, > it arrived in my box. (It had the usual "sprayed-on” zebra/barcode > representing the ZIP+4 along the bottom to facilitate machine-reading > further along the pipeline that all our other mail has, too, but was > otherwise addressed with “only the ZIP+4”). > > Three points about ZIP codes which might be similar to postcodes in > Australia (and Canada and the UK, it seems): despite what most people > think, ZIP codes are NOT required for a letter to be delivered. It might > take a bit longer without one, but it WILL be delivered. City, State, > ZIP? (Or ZIP+4?): not really required, as City, State (only) does > suffice. Secondly, I’ve discerned (and had others who should know confirm) > that a ZIP code is much like a “routing algorithm” (of 5, 9 or 11 digits): > it is NOT a geographic area that can be (easily) described by a polygon, > even a multipolygon. I mean, plenty of cartographic gymnastics have made > geographic areas OUT OF ZIP codes (or postcodes) — some relatively > “successfully” (accurately?) but they are not such things (a geographic > area, even as they seem as though they are). > > Finally, the whole thing about “these are the property of the post office > and we’re going to be very non-sharing with them…” seems to be widespread > with postcodes, I’m not sure why that is, but hey, if postal services want > their codes to be proprietary, they can do that. But that should make > cartographers like us think twice about why we’re including them in a map: > what, exactly, can putting these data in OUR map “buy” us by doing so? > Yes, I know there is a general attitude of “postcodes are NEEDED, else how > will the mail get delivered!” (thought in our mind’s voice approaching a > shrill panic). But, recall, (at least in the USA, maybe Australia, Canada, > UK..., too) they aren’t strictly needed, but are more of a convenience for > automation and the internal workings of how to sort and deliver mail, not > really a function a map needs to provide its consumers (anyway). > > Things to think about, and perhaps quite non-overlapping, but I felt like > typing all that, so thanks for reading. > _______________________________________________ > Talk-au mailing list > Talk-au@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-au >
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