I recently used What3Words to give a friend my house's location, since our entire neighborhood is only distinguished by the second address line, and Google Maps doesn't actually know any of them. W3W can redirect to Maps with a lat/long which works correctly for directions.

Afterwards, I spent part of the weekend thinking, as one does, about the tradeoffs of the two major "make every part of Earth addressable" efforts: What3Words and Google's PlusCodes.

The two made some very interesting tradeoff decisions differently, and I'm not sure which I like better!

What3Words

W3W divides the world up into ~3m squares, and assigns each a 3-word name. For example, I am at this very moment sitting at my office desk, located in the square named ///jukebox.slang.leaned. You can pop that triplet at the end of "what3words.com/" and find my precise location.

The assignment algorithm is proprietary (that's how they make money), but it's designed to (a) make more populated areas use shorter words, and (b) make nearby areas have no relationship to each other.

That is, there is absolutely no relationship between the name of one square and the name of the next square over; they're effectively random.

The intentional benefit of this is that if you get the name slightly wrong, you'll get the address WAY wrong, and will hopefully notice that the directions to your friends house shouldn't be directing you to another country. No "near misses" just putting you on a nearby street.

Obvious downside is the same, tho - errors will get the address way wrong, rather than nearly correct. It also means you can't generalize to larger areas; there's no concept of resolution larger (or smaller) than the 3m base square.

So you can't give an approximate location, only a fairly precise one. That said, on the scale that most ordinary people want, that's fine; we already have meaningful spatial demarcations that serve that purpose well (town/city names, plus maybe directional words or neighborhoods).

While the first version of W3W specifically used English words, they've since produced a large number of localized versions, so people can share addresses in their own language. They all use the same grid, so you can provide your location in multiple languages if you're expecting to serve a multilingual community.

PlusCodes

They're literally just a more usable way to express lat/long coordinates. Rather than base-10 (useful for math) they use base-20 (useful for memorization/communication), and interweave the digits so you get more precise in both dimensions as you go along.

That is, the first and second chars of a plus code are the high-order lat and long, naming a 20 degree square slice of the Earth. The third and fourth narrow that down to a 1 degree square (roughly 60 miles). Fifth and six cut it to a .05 degree square (roughly 3 miles). Etc. This goes on for 10 digits at which point they switch to a different scheme that goes digit-by-digit, but the details don't super matter.

Between the 8th and 9th digit you use a + to break it up visually, like 6PH57VP3+PR. You can also drop the first four digits if you have a city name or similar, like "7VP3+PR6 Singapore", giving you an easier-to-remember 7-digit name for an approximately 3m square area.

Benefits here are

• easy to compute, obviously, since it's just lat/long expressed in base 20 and interwoven. The encoding/decoding algos can be done from scratch in a hundred lines or less of code. No need to contract out decoding to a 3rd-party company.
• the precision can be scaled up or down trivially by adding or removing digits. (If you remove digits before the +, you replace them with 0, which isn't otherwise a valid digit in a pluscode.) So you can indicate large areas (so long as they're reasonably approximated by the slice boundaries), or even much smaller, more precise areas.
• if you forget, or just leave off, the last bit of the code, you'll still end up close by. Like, a neighborhood can generally be located without any digits past the +.

Big downside is that getting anything but the very end wrong can make the address quite wrong without it necessarily looking wrong. In other words, errors in the pluscode translate to vastly different scales of errors in the final location, depending on where the error occurs. The most obvious errors (pointing to an entirely wrong part of the world) generally aren't even possible since those digits are usually omitted in favor of specifying a city instead, so your errors will often still give a location that looks reasonable at first glance, but might be next door, next neighborhood over, or next city over.

Another downside is the code spends the same amount of entropy on each location no matter how populated or middle-of-the-ocean it is. The one nod to this is being able to shorten the standard code from 11 digits to 7+city name (effectively giving human-friendly names to the 4-digit-prefix blocks), but past that there's no distinction between "populated city" and "wilderness", which W3W does distinguish between.

Both Are Cool

So there's several tradeoffs on either, several of which place the two on directly opposed sides. I dunno which I like best! Maybe both are great! I think that maybe they're best for different use-cases.

I think W3W does end up slightly better for human-relevant locations, such as in cities. The "any error is obviously way wrong" behavior seems like a benefit to me over the "error ranges from very slightly to very extremely wrong, depending on where it occurs" behavior of PlusCodes. And I like that populated areas are favored with shorter, more common, easier-to-spell words. (Compare my location I stated above, ///jukebox.slang.leaned, with an ocean square just a mile or so off the coast near me, ///virtuously.daylight.facsimiles.)

Also, when you are naming a larger area, like your house (rather than a very specific area like your front door) you have a goodly number of choices to pick from, and can choose one that's particularly memorable or appropriate. For example, I have about 20 squares covering my house, and chose a nice tech-related one (which I won't share, since my address isn't easy-accessible public knowledge and I'd prefer to keep it that way if I can) that happens to land roughly in the middle of my living room.

On the other hand, scientific use-cases seems to better served by PlusCodes. The variable slice sizes you can name means you can address many different use-cases, like naming ranges or geographic areas, as well as very precise locations, and can get more precise than the 3m square too, just by appending more digits. The names also all look generically similar, rather than having the potential for humor, which can be both good and bad in professional settings. (The 20-character set used by PlusCodes was chosen both to reduce the chance of mistyping/mishearing them, and to minimize the chance of addresses being real words, rude or otherwise. For example, it's missing all the vowels.)

Anyway I just wanted to get some of these thoughts out, and to interest more people in either/both of these systems if they weren't already aware. If you read to this point, success!