Watch-chronometers

[prv]

Dont understand all this. There are no end of gaskets on my boat but they are all where they should be inside the two engines.

http://en.wikipedia.org/wiki/Gasket_(sailing)

HTH

Pete

 

[JayBee]

Pete - something wrong with the second bracket around (sailing) in your link.

 

[alan_d]

http://en.wikipedia.org/wiki/Gasket_(sailing)

HTH

Pete

Should be http://en.wikipedia.org/wiki/Gasket_(sailing)
[Final bracket before the /url tag]

 

[prv]

Pete - something wrong with the second bracket around (sailing) in your link.

Ta - fixed. No idea how that happened, I pasted the link as a whole into the dialogue box rather than coding it myself. Bug in the forum I guess.

Pete

 

[Cruiser2B]

GPS clocks don't necessarily show UTC; the satellites don't always take account of leap seconds. Also, a navigational GPS always has a delay in it; the time display is not necessarily in sync with the GPS time. The delay can be up to 2 seconds. GPS can be a very precise source of time, but only if the receiver is optimized for time processing; it is used in this way for network time servers, for example. But the GPS on your boat isn't optimized in that way, so it can be seconds off.

Thanks. There seems to be a good write-up in Wikipedia:

While most clocks are synchronized to Coordinated Universal Time (UTC), the atomic clocks on the satellites are set to GPS time (GPST; see the page of United States Naval Observatory). The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain leap seconds or other corrections that are periodically added to UTC. GPS time was set to match Coordinated Universal Time (UTC) in 1980, but has since diverged. The lack of corrections means that GPS time remains at a constant offset with International Atomic Time (TAI) (TAI – GPS = 19 seconds). Periodic corrections are performed on the on-board clocks to keep them synchronized with ground clocks.[91]

The GPS navigation message includes the difference between GPS time and UTC, which as of 2011 is 15 seconds because of the leap second added to UTC December 31, 2008. Receivers add this offset to GPS time to calculate UTC and specific timezone values. New GPS units may not show the correct UTC time until after receiving the UTC offset message. The GPS-UTC offset field can accommodate 255 leap seconds (eight bits) that, given the current period of the Earth's rotation (with one leap second introduced approximately every 18 months), should be sufficient to last until approximately the year 2300.

I set my watch by the official time signal, but often compare it with the GPS and it's always been close enough for government work

 

[Kukri]

I do carry a mechanical deck watch, which I rate by reference to the GPS. It's the easiest way of doing it, since they are both handy to the chart table, Since my sextant observation skills are pretty coarse I am not too worried by a couple of seconds.