3 ms·
From https://en.wikipedia.org/wiki/GPS#Timekeeping https://en.wikipedia.org/wiki/GPS#Timekeeping : GPS time is theoretically accurate to about 14 nanoseconds.
by adrianb 12y ago
From https://en.wikipedia.org/wiki/GPS#Timekeeping https://en.wikipedia.org/wiki/GPS#Timekeeping :
GPS time is theoretically accurate to about 14 nanoseconds. However, most receivers lose accuracy in the interpretation of the signals and are only accurate to 100 nanoseconds.
- easytiger 12y agoFor phones to achieve that the GPS would have to be turned on & synced near constantly. Also the accuracy goes down with mobile devices and new strategies have to be applied given the change in altitude and greater temperature flux. It also depends on the phone's internall oscillator & the gps recv unit used. Mobile phones use CDMA stuff to sync their clocks, not GPS
- pjc50 12y agoGSM phones are supposed to be able to pick up "NITZ" (network information and time zone") messages, but these aren't reliably sent by most networks. In practice, smartphones get it over NTP like everyone else and dumbphones have user-set time that may, if you're lucky, be synced by counting the base station's time slot intervals.
- easytiger 12y agoYes modern smartphones often hardcode ntp servers and prob do ineffective hard resetting. Would be good to know more how they do it.
- enf 12y agoThings have changed a bit since the last time I had anything to with it, but you can read the Android source code: https://github.com/android/platform_frameworks_base/blob/master/services/java/com/android/server/NetworkTimeUpdateService.java https://github.com/android/platform_frameworks_base/blob/mas... NITZ is terrible. You only get one-second accuracy, a GMT offset, and a DST flag, and they can all be wrong at the whim of someone at the phone company.