GPS positioning (Global Positioning System) will be on April 6, 2019 through & ldquo; zero & rdquo;, to meet the new cycle. Recently, at the RSA U.S. Information Security Forum, which held its general meeting in San Francisco, some experts predicted that the old GPS system will cause an error similar to the computer millennium bug on April 6; and more authoritative experts on security expressed that they would never take an airplane on that day ……;.
GPS positioning & ldquo; to zero & rdquo; in fact is & ldquo; GPS weekly flip & rdquo; the popularization of the expression, the United States civil type GPS service interface committee (CGSIC) not long ago announced a notice, GPS whole weekly counting value will be on April 6, 2019 at 24:00 by 1023 into 0, called GPS weekly flip.
The emergence of the situation with the interface design of the GPS system at that time related to this time, the GPS system as an international navigation and positioning timing center system, at the beginning of the design program created a whole set of time period system, called & ldquo; GPS time & rdquo;; and this together with the point of matching the UTC time period (UTC) of January 6, 1980 at 0:00 hours. Because to achieve the purpose of timing, then the GPS system uses the navigation data signal to continuously broadcast to the user at this stage of the time to match the GPS time, the system design staff to use the weekly count (WN) and the weekly seconds (TOW) to jointly express the present moment from the GPS initial value of the time difference, and therefore combined with the leap second to obtain the present UTC moment, the success of the time.
Due to various reasons, GPS at the beginning of the design program, the design program staff only used 10bit to characterize the WN, resulting in WN must be in 0—1023 each other cycle. When WN from 1023 into 0, will produce GPS weeks flip, appear to usher in a new week of expression. 1024 weeks match to the annual time period of about 19.7 years, from the GPS system when the starting moment counting from the last GPS weeks flip is August 21, 1999, this time it happens to be April 6, 2019, November 20, 2038 will appear the next time! GPS Week Flip.
The impact that will be caused
GPS receivers that have not been pre-processed for the GPS weekly flip will cause the receiver's output time period to go back to roughly 19 years ago. This may have an impact on any system or application that relies on GPS timing. It is noted that in civil aviation, timing is basically done by relying on satellite navigation systems, and all automated equipment is benchmarked against that time. As a result, weekly flips may trigger confusion in ATC radar signal data, which can cause problems such as data disruption and target tracks not correlating with plans.
At the same time, the exchange of information between meteorological equipment may not be automated due to time jumps in the alignment of meteorological information, resulting in difficulties in weather forecasting, which may affect flight scheduling and cause unnecessary losses. In addition, the use of receivers that do not do the GPS week number flip process for timing will also have an impact on some automated operation infrastructure areas, such as the BITS system used in the power, communication and financial sectors. If the BITS system only refers to the GPS timing signal, it may cause the system to be paralyzed and so on.
Solutions
In order to avoid the impact, industries should contact GPS receiver suppliers in advance to inquire whether there is any timing error problem due to GPS week number flipping, and make a good plan and simulation test.
As for China's BeiDou system, there is also the problem of BD weekly count flip, but when designing, its weekly count is expressed in 13bit, and the flip period is 8,192 weeks, which is about 160 years, thus effectively avoiding the problem. However, as long as the satellite navigation system has the problem of week number flip, just the cycle time is not the same.
