[g_p]

In addition, the user knows their own location by virtue of having access to a GPS device - for W3W to work they've used a GPS and it's really just an in-band voice protocol for exchange of location.

It strikes me that W3W will eventually be replaced by the emergency location standards built into mobile which effectively SMS your location to the control centre on starting the call. Then there's little need for voice based W3W exchange - at best it could be a dialogue between caller and call handler to confirm the approximate area and location, and to take details like (for urban environments) if it's an apartment block or house etc. Or off the beaten track, which side of the mountain route they walked up to reach their current location.

[bellyfullofbac]

The few times I've accidentally called emergency services, my Android phone asks me first if I want to allow the phone app to access my location...

It would've been more logical to automatically share it, to be honest...

[blkhawk]

maybe some type of encoding that sends it via audio. Would probably be the most robust way plus you can use the same encoding everywhere no matter the communication medium or cell net support.