5/17/2023 0 Comments Gps time converter![]() ![]() Nevertheless, the Control Segment does not constantly tweak the clocks in the satellites to keep them perfectly on GPS time. These effects cause the satellite's clocks to not oscillate perfectly. They're not perfect timekeepers, and they're affected by several things, moving in and out of the shadow of the Earth, gravitational changes, and so on. However, the oscillators (clocks) in satellites have a tendency to drift. The Control Segment keeps track of time and uploads clock corrections to the satellites. It takes more than a portion of the NAV message to define those relationships to the necessary degree of accuracy. But because the time relationships in GPS are changing constantly, they can only be partially defined in these subframes. ![]() The NAV message also contains information the receiver needs to come close to correlating its clock with that of the clock on the satellite. In this area, subframe 4 can accommodate 8 bits, 255 leap seconds, which should suffice until about 2330. Information in subframe 4 of the NAV message includes the relationship between GPS time and UTC, and it also notes future scheduled leap seconds. ![]() For example, GPS time was 16 seconds ahead of UTC on Jand 18 seconds ahead of UTC on September 11, 2020 So, even though their rates are virtually identical, the numbers expressing a particular instant in GPS Time are different by some seconds from the numbers expressing the same instant in UTC. Since then, many leap seconds have been added to UTC, but none have been added to GPS Time. Nevertheless, there was a moment when GPS Time was identical to UTC. However, leap seconds are not used in GPS Time. In other words, the rate of UTC is consistent and stable all the time, but the numbers denoting the moment of time changes whenever a 1-second leap second is introduced. Therefore, in order to keep the discrepancy between UTC and the earth’s actual motion under 0.9 seconds, corrections of 1 second, called leap seconds, are periodically introduced into UTC. In fact, it is more stable than the rotation of the earth itself, such that UTC and the rotation gradually get out of sync with one another. It is steered by about 65 timing laboratories and hundreds of atomic clocks around the world and is remarkable in its stability. The rate of UTC itself is carefully determined. The exact difference is in two constants, A0 and A1 in the NAV message, which give the time difference and rate of system time against UTC. Specifically, the rate of GPS Time is kept within 1 microsecond, and usually less than 25 nanoseconds, of the rate of Coordinated Universal Time (UTC). The rates of these two standards are virtually the same. Coordinated Universal Time is the time standard for the world. It is also known as GPS System Time (GPST). GPS Time is the time standard of the GPS system. One of them is GPS Time and the other is Coordinated Universal Time (UTC). The information in subframe 4 helps a receiver relate two different time standards to one another. There is time-sensitive information in the NAV message in both subframe 1 and subframe 4. ![]()
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