3 ms·
An error of 7 meters would probably mean the FAA would refuse to certify GPS for aircraft use. Even now it's only usable in many circumstances with ground based
by frisco 10y ago
An error of 7 meters would probably mean the FAA would refuse to certify GPS for aircraft use. Even now it's only usable in many circumstances with ground based corrections (eg WAAS or GBAS). A minute of error would probably make it unusable for enroute navigation.
- creeble 10y agoI'm sure someone will point it out, but GPS doesn't use leap seconds. "Adding leap seconds is a waste of time" I see what you did there. And agree!
- frisco 10y agoInteresting. I didn't know that. I think half of the point remains (what sounds like a small error can be critical) but I guess GPS isn't a great example, then, as safety critical systems tend to be smarter by design anyway.
- brudgers 10y agoThe safety critical systems don't reset their clocks because safety critical systems maintain independence in order to maintain safety. Safety critical systems are a place where the abstraction of a Terran Year as a cosmological constant breaks down.
- cnvogel 10y agoGPS is indeed happily unaware of leap seconds, it started counting seconds on January 6th, 1980 (UTC) {1 week is 604800s, weeks count 0..1023, there already was one rollover}. http://imgur.com/a/uq6D0 http://imgur.com/a/uq6D0 A few minutes ago, when the screenshot was taken, this was second #501074 in week #1928. As a courtesy to users, GPS transmits the current number of leap-seconds inserted in UTC (currently: 17) and the fact that a leap-second will be inserted the next occasion (end of this year: "LEAP PENDING!"). That's of course very helpful when you are using GPS disciplined clocks for timekeeping.
- brudgers 10y agoThe error would be in celestial navigation not GPS. The frame of reference for a satellite orbiting the earth is the same as the edge of the landing strip.