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The phrase "does not account for leap seconds" is highly misleading. Sure, the internal GPS time does not include leap second, but the GPS system also broadcast
by segfaultbuserr 4y ago
The phrase "does not account for leap seconds" is highly misleading. Sure, the internal GPS time does not include leap second, but the GPS system also broadcasts the leap second offset for conversion to UTC. Also, before a leap second adjustment is made, it also generates leap-second announcements.
<flame>IMHO, in the perfect world, this is how the leap second should have been handled in all computer systems. The international atomic time (TAI), without leap second, should be used for internal timekeeping in computers. The UTC leap second adjustment should be handled as an external offset, similar to timezone data.</flame>
- brandmeyer 4y agoHear, hear! Galileo and BeiDou behave similarly to GPS in this respect. Oddly enough, all three time bases have an origin that is specified in UTC, but model elapsed seconds since that epoch. So GPS time does include the 9 leap seconds which occurred prior to its epoch. Galileo time's epoch is aligned to the GPS week, so it shares a leap second offset with GPS, but its still specified in terms of UTC (1999-08-21T23:47). BeiDou's epoch is specified as 2006-01-01T00:00 UTC, so it includes another 14 leap seconds with respect to GPS. So the three systems do not quite model the platonic ideal, but fortunately the offsets are all constants and its trivial for the receiver to use such an ideal in practice. GLONASS time is UTC + three hours (ie, Moscow civil time) and does have leap seconds. To figure out the leap second offset between GLONASS time and GPS time the GLONASS ICD actually tells you to get that info from the GPS broadcast messages, although they do have an alert system for upcoming leap second updates. One more reason to dislike working with GLONASS.