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Re: Differences between GPS and WWV time
From: UNK
Date: 2001 Jun 22, 1:26 PM
From: UNK
Date: 2001 Jun 22, 1:26 PM
Robert Owens [mailto:tugly@NEOSOFT.COM] asked: > Has anyone noticed a difference between GPS and WWV time. I hear some units > display a different time depending on software. The GPS system broadcasts time as a week number (where Week 0 began at 00:00:00 6 Jan 1980 UTC) and seconds-of-week. Somewhere else in the broadcast message is the current difference between this strict sequential count and UTC, since UTC has had a dozen or so leap seconds inserted since the beginning of the GPS epoch. All but the most primitive receivers correctly apply the leap second correction. However, as Dan Allen noted, receivers' internal clocks often drift, and shouldn't be trusted until the unit is tracking. An interesting variation on the "Y2K Bug" of recent memory was GPS week roll-over. The week field is 10 bits long, so in August 1999 it rolled over from week 1023 to week 0. Some early GPS receivers needed software updates or some other intervention in order to cope. -- Peter
