[time-nuts] Time transfer, internationally before GPS

Bob Camp lists at rtty.us
Tue Mar 4 07:44:20 EST 2014


Also consider that the “trip” was not very quick. They were a: spend day or three here, go there (day of travel), spend several days someplace else, move on to next location. Eventually you returned the clock to it’s starting point. The “trip” was only good to something related to the drift of the Cs. 

If the clock as it bounced around was good to 1 ppt, that’s 86 ns per day. If the trip was 10 days long, there’s a good chunk of a microsecond involved. If you go back into the FCS or PTTI proceedings you can find the data. They spent a lot of time on data reduction after the trip. Desk time was cheap compared to travel time. I don’t think you will find numbers under a few hundred ns claimed for these sort of multi site, many days crossing oceans trips.


On Mar 3, 2014, at 11:04 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:

>> The piece didn't say anything about correcting for acceleration.
> Hi Max,
> True, but at one point the video mentioned microsecond resolution, and at that level, no relativistic corrections for airplane trips are needed.
> If you want to get down to nanoseconds, then yes, you will want to apply altitude (gravitational), velocity, and Sagnac corrections.
> You can use my rel.exe tool (www.leapsecond.com/tools/) to calculate the two relativistic effects:
> C:\tvb> rel 35000ft 500mph 8hr
> ** Altitude 10668.000 m (35000.000 ft, 6.629 mi) 1.161e-012 blueshift
>     4181.381949 ps/hour
>      100.353167 ns/day
> ** Velocity 223.520 m/s (804.672 km/h, 500.000 mph) -2.779e-013 redshift
>    -1000.607783 ps/hour
>      -24.014587 ns/day
> ** Net effect (GR+SR) 8.835e-013 shift
>     3180.774165 ps/hour
>       76.338580 ns/day
> ** Duration 28800 seconds (8.000 hours, 0.333333 days)
>    25446.193322 ps total
>       25.446193 ns total
>        0.025446 us total
> So for an 8 hour flight at 500 mph at 35,000 feet the time dilation correction is only about 25 ns.
> Add to that the Sagnac correction for East-West or West-East travel between USNO and NPL, about +/- 22 ns.
> /tvb
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