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| author | Sanjeev Gupta <ghane0@gmail.com> | 2015-03-16 02:01:18 +0800 |
|---|---|---|
| committer | Gary E. Miller <gem@rellim.com> | 2015-03-15 12:45:22 -0700 |
| commit | d54d77a3ad68072784628dbce50cb5027612af27 (patch) | |
| tree | b4fb6488c39f8a27b57237bcf96b7b4be7089efd /www | |
| parent | 87b5f1d8540141386742b302cc91b63a4a1a4d90 (diff) | |
| download | gpsd-d54d77a3ad68072784628dbce50cb5027612af27.tar.gz | |
Update and cleanup the Time Sources section
Add refernce to BIPM Circular T (not WWWB)
UTC(NIST) tracks UTC to less than 5ns
Signed-off-by: Gary E. Miller <gem@rellim.com>
Diffstat (limited to 'www')
| -rw-r--r-- | www/time-service-intro.txt | 19 |
1 files changed, 11 insertions, 8 deletions
diff --git a/www/time-service-intro.txt b/www/time-service-intro.txt index 5f47210f..6aca5c7c 100644 --- a/www/time-service-intro.txt +++ b/www/time-service-intro.txt @@ -45,17 +45,18 @@ oscillator (popularly called an "atomic clock") used as a source standard by a national time authority. By international agreement, the U.S. and other major national time authorities use primary standards based on electronic transitions between the two hyperfine -energy levels of the ground states of cesium-133 atoms. +energy levels of the ground states of Cesium-133 atoms. -National time standards are synchronized (essentially, averaged) to +National time standards are synchronized (essentially, averaged after +removing outliers and consistent errors) to yield an international reference called Universal Coordinated Time. -National time standards, including the U.S.'s, are normally considered -accurate to UTC within 20 ns <<WWVB>>. +The US National time standard, UTC(NIST), normally tracks +UTC to within 5 ns <<BIPM-T>>. -U.S. atomic clock time is propagated through the GPS system, which -enables receivers to generate a pulse-per-second signal ("1PPS" or -just "PPS") accurate to the top of the current UTC second within 50 -ns. +U.S. atomic clock time (UTC(NIST)) is propagated through the GPS +system, which enables receivers to generate a pulse-per-second +signal ("1PPS" or just "PPS") accurate to the top of the current +UTC second within 50 ns. National time standards are also propagated through time radios. In the U.S., digital time signal is provided by WWVB in Colorado, driven @@ -264,6 +265,8 @@ Procedures] - [[[WWVB]]] http://tf.nist.gov/timefreq/pubs/bulletin/pdf/1999OCT_TF_BULLETIN.pdf[NIST Time and Frequency Bulletin NISTIR 5082-10] +- [[[BIPM-T]]] ftp://ftp2.bipm.org/pub/tai/publication/cirt/[See latest Circular T from BIPM] + - [[[WWVBMAP]]] http://tf.nist.gov/stations/wwvbcoverage.htm[WWVB Coverage Area] - [[[SPECTRUMWIKI]]] http://www.spectrumwiki.com/wiki/DisplayEntry.aspx?DisplyId=51[Low Frequency Time Signals] |