[talk-au] The Paradox of Postcodes (Was Re: Victorian Vicmap Address Import Proposal - Suburb and Postcode discussion)

[Adam Horan]

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 <steveaOSM at 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.
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