3 ms·

If you drop a pin in google maps it shows you the lat/lon, e.g. 51.5010392, -0.1423616 7 decimal places of lat/lon is approximately a centimetre.

mjlee 2y ago
To save some maths during a crisis - 3 is ~100m, 4 is ~10m.
- HPsquared 2y ago
  Lat/long coordinates and metres are actually linked quite closely: the metre was originally defined as "the arc from equator to North pole is defined as 10,000 km". That is, 90 degrees is 10,000 km.
  - jameshart 2y ago
    And if the French had had their way, we’d use grads not degrees and latitude would instead be 100 grads per 10,000km, so each grad of latitude would be 100km. That kind of sanity was, of course, unacceptable to the rest of the world.
    - HPsquared 2y ago
      The French were really into decimalization for a while. They tried decimal time (10 decimal hours per day, each 100 decimal minutes, each 100 decimal seconds), and a new calendar with equal 30-day months (the extra days at the end were national holidays, in September in the Gregorian calendar). Also 10-day 'décades' instead of weeks.
growse 2y ago
Or a plus code, which is a little less precise, open, and a little easier for humans to transmit than a latlng.
_trampeltier 2y ago
Centimetre, and after the next big earthquake are all numbers off, sometimes even by several meters. Now what you do? New addresses for all, or wrong numbers to new buildings?
- simonbarker87 2y ago
  Not really a problem in the UK
- xnorswap 2y ago
  This was in the context of needing to give a location for an ambulance, not for addressing things. It's an ephemeral location for an ephemeral need.
- krisoft 2y ago
  > Now what you do? When the ambulance arrives wave your hands and say "over here!". So they can do the "last several meters" of navigation by homing on your visual presence.
- bluGill 2y ago
  In the best case your GPS is off by far more than the worst case GPS. There are GPS receivers that can get you to within 2cm, but they cost thousands of dollars and are not used in phones. In the context of navigation that is good enough - if you are within 100 meters you can look to see your destination.

mjlee 2y ago

To save some maths during a crisis - 3 is ~100m, 4 is ~10m.

HPsquared 2y ago
Lat/long coordinates and metres are actually linked quite closely: the metre was originally defined as "the arc from equator to North pole is defined as 10,000 km". That is, 90 degrees is 10,000 km.
- jameshart 2y ago
  And if the French had had their way, we’d use grads not degrees and latitude would instead be 100 grads per 10,000km, so each grad of latitude would be 100km. That kind of sanity was, of course, unacceptable to the rest of the world.
  - HPsquared 2y ago
    The French were really into decimalization for a while. They tried decimal time (10 decimal hours per day, each 100 decimal minutes, each 100 decimal seconds), and a new calendar with equal 30-day months (the extra days at the end were national holidays, in September in the Gregorian calendar). Also 10-day 'décades' instead of weeks.

growse 2y ago

Or a plus code, which is a little less precise, open, and a little easier for humans to transmit than a latlng.

_trampeltier 2y ago

Centimetre, and after the next big earthquake are all numbers off, sometimes even by several meters. Now what you do? New addresses for all, or wrong numbers to new buildings?

simonbarker87 2y ago
Not really a problem in the UK
xnorswap 2y ago
This was in the context of needing to give a location for an ambulance, not for addressing things. It's an ephemeral location for an ephemeral need.
krisoft 2y ago
> Now what you do? When the ambulance arrives wave your hands and say "over here!". So they can do the "last several meters" of navigation by homing on your visual presence.
bluGill 2y ago
In the best case your GPS is off by far more than the worst case GPS. There are GPS receivers that can get you to within 2cm, but they cost thousands of dollars and are not used in phones. In the context of navigation that is good enough - if you are within 100 meters you can look to see your destination.