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Diffstat (limited to 'www/gpsd-time-service-howto.adoc')
| -rw-r--r-- | www/gpsd-time-service-howto.adoc | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/www/gpsd-time-service-howto.adoc b/www/gpsd-time-service-howto.adoc index 3bee4720..c4ae7553 100644 --- a/www/gpsd-time-service-howto.adoc +++ b/www/gpsd-time-service-howto.adoc @@ -137,12 +137,13 @@ second and the following subframe broadcast. GPS date and time are subject to a rollover problem in the 10-bit week number counter, which will re-zero every 1024 weeks (roughly every 19.6 -years). The last rollover (and the first since GPS went live in 1980) -was in Aug-1999; the next will fall in Apr-2019. The new "CNAV" data +years). The first rollover since GPS went live in 1980 was in Aug-1999, +followed by Apr-2019, the next will be in Nov-2038 (the 32-bit and POSIX +issues will probably be more important by then). The new "CNAV" data format extends the week number to 13 bits, with the first rollover occurring in Jan-2137, but this is only used with some newly added GPS signals, and is unlikely to be usable in most consumer-grade receivers -prior to the 2019 rollover. +currently. For accurate time reporting, therefore, a GPS requires a supplemental time references sufficient to identify the current rollover period, |