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Better: USB GPS receiver with the NMEA 0183 GPZDA sentence sent at least once a second. The developer of the Windows software NMEATime2 recommends GPS units with the U-blox 7 receiver, [4] and this software uses a control loop to analyze the text of the GPS timing sentence, and claims to achieve 1 ms accuracy with the technique.
The GPS navigation message includes the difference between GPS time and UTC. As of January 2017, GPS time is 18 seconds ahead of UTC because of the leap second added to UTC on December 31, 2016. [156] Receivers subtract this offset from GPS time to calculate UTC and specific time zone values. New GPS units may not show the correct UTC time ...
This is a list of the UTC time offsets, showing the difference in hours and minutes from Coordinated Universal Time (UTC), from the westernmost (−12:00) to the easternmost (+14:00). It includes countries and regions that observe them during standard time or year-round.
Nearly all UTC days contain exactly 86,400 SI seconds with exactly 60 seconds in each minute. UTC is within about one second of mean solar time (such as UT1) at 0° longitude, [14] (at the IERS Reference Meridian). The mean solar day is slightly longer than 86,400 SI seconds so occasionally the last minute of a UTC day is adjusted to have 61 ...
Of the only two other systems aiming for global coverage, Galileo calculates from an epoch and BeiDou calculates from UTC without adjustment for leap seconds. [5] [needs update?] GPS also transmits the offset between UTC time and GPS time and must update this offset every time there is a leap second, requiring GPS-receiving devices to handle ...
The second rollover occurred on the night of April 6 to 7, 2019, when GPS Week 2,047, represented as 1,023 in the counter, advanced and rolled over to 0 within the counter. [2] The United States Department of Homeland Security, the International Civil Aviation Organization, and others issued a warning about this event.
Thus, GPS time is ahead of UTC by an integer (whole) number of seconds. The P code is public, so to prevent unauthorized users from using or potentially interfering with it through spoofing , the P-code is XORed with W-code , a cryptographically generated sequence, to produce the Y-code .
The GPS time scale has a nominal difference from atomic time (TAI − GPS time = +19 seconds), [11] so that TT ≈ GPS time + 51.184 seconds. This realization introduces up to a microsecond of additional error, as the GPS signal is not precisely synchronized with TAI, but GPS receiving devices are widely available. [12]