I don't see the relevance of that complaint. People don't memorize their current lat long to 16 sig figs either. You'd still need a gps device or a paper map without w3w.
EDIT: Also, given a set of lat/long coordinates, regardless of the precision, you could infer their spatial relationship as well.
For great circles the metric ratio is close to 40000km/360. A simple trick would be converting to 400gon first¹, but even using 111 Km per degree is a useful approximation.
So 0.01 decimal degree difference in latitude is always 1.11km or roughly 1km. All you need to remember is your length of 1 degree longitude at given latitude which is the following basic trigonmetric relation:
0.01deg = cos(lat) * 1.11km
Cheap linear approximation will do well here too. In South to North order: So usually factor down to 0.8 to 0.7 (38 to 48 Miles) if you live anywhere in the continental US. For Europe it's 84km in Rome, 72km in Paris, 69 in London, 67 in Berlin and 56km in Stockholm
And for approximating local distances it's simply those metric deltas with pythagoras, no need for Haversine or even non-spherical earth models here.
The most important relation for anyone who is into earth and the metric system, is that it's 10M meters or 10,000 km from pole to equator per original definition. You dont even need to remember the earth radius, since that's also defined by 4x10,000km/2π historically.
¹It's a shame that the metric revolution stopped short of Gradians, when it comes to full metric convenience here.
https://en.wikipedia.org/wiki/Earth%27s_circumference#Histor...
Don't overestimate that. There are nasty exceptions where the street disappears and continues elsewhere without a significant gap in house numbers, especially in cities with a long history.
Either way, it does work for several billion other people.
Even granting that your “nasty exceptions” comprise fully half of all complete addresses, that would simply mean that a normal addressing scheme is better than W3W 50% of the time and no worse in all other cases.
A common feature of most addressing systems is being able to infer relative distance - this is usually true of even street address. (Yes, I am aware this is not always true, and yes, I am aware there are hilarious counter-examples. I don't think that changes the point.)
There's also the old country directions method - navigate by Landmarks. If your emergency services operator is familiar with the geography of their area, this becomes much easier. If you are similarly familiar, this can be very quick.
"Timmy fell down the well by the old mine on the edge of town! Good girl, Lassie."