> More importantly, satellite positioning receivers need a cached "ephemeris" file that helps them predict which satellites will be overhead at a given time to operate efficiently, accurately, and quickly.

Interesting, I've never heard of that particular optimization for GNSS before. I know GPS transmits ephemeris information in each frame, since that's the input data for the positioning calculations. I've got a number of Garmin watches, and they've always been able to get a position fix even after being disconnected for weeks.

I find GNSS implementations very interesting, which manufacturer is making their watches like this?