Where does your NTP server get is time from?

I’d like to say that it reads the NMEA stream from my GPS device, but unfortunately it doesn’t I simply followed the advice given on the joining the pool page:

The servers joining should not have pool.ntp.org as their upstream server(s), but should configure some good servers manually (those servers may be chosen from the pool. The point is that they are chosen statically instead of assigned randomly at each server restart. This will help providing an acceptable quality of service.)

and so chose eight machines from the Stratum 2 list they linked to that had an open access policy. I also tried to mix up the continents they serve from, in the hope that links out of the UK won’t all suffer simultaneous access failure.

I may look at getting a local time source in the future, but I’ve already had to change my ADSL router as the NTP packets were killing the last one more than once per day and it wouldn’t come back by itself (as my history graph showed) – the new one will at least auto-reset but still dies multiple times per day I might have to get a PPPoA / PPPoE bridge and do the login via one the servers, as it’s looking tricky to find an ADSL box that will do multiple IP’s properly.