NavList:

Thank You all for info re GPS-timekeepers. Ongoing and previous discussions/explanations.

I have noticed that the clock (displayed value for user) on my handheld Garmin sometimes stops for a second or two, then jumps back to correct time. Can be explained by the "low priority" attitude within the machine. OK, I buy that easily.

 

What I do not understand is the fact that the GPS on the sailing training vessel I worked on after restart "woke up" on correct time, but after a while (substantially longer than the recommended 15 minutes)  gave faulty information (up to 20 seconds). Surely it would have had time enough to correct itself.

A few seconds plus or minus would not mean any catastrophic result in LOP's or positions derived from astrosights, but 20 seconds is more than acceptable and I take the experience with me and double check time before I really need high precision (like when taking sights).

Again, thank you for taking your time on this subject.

 

PS: Ref iPhone-navigation: I do not think it is possible (for a normal user) to adjust the time presentation to HHMMSS or presenting the GPS position in the form DDMM,mm. I use an app called "Pilot Time" for time. App's like the ones from Navionics charts (for iPhone) show positions in the navigation format of DD-MM,mm.DS.

 

Best -

Magnus Sjoquist

N 58-20,213 / E 015-43,668 (iPhone 3GS with Navionics)

Written at 08-48-55 UTC/GMT/ZULU (iPhone with Pilot Time)

("Better roughly right than exactly wrong").

 

 

 

Den 09 feb 2012 kl 22:31 skrev Alan S <alan202@verizon.net>:

Magnus:

I had earlier mentioned the Casio brand G-Shock "Atomic Watch". The one I have, my second, the band failed on #1, and Casio replaced the watch, guess that that was a cheaper alternative compared to replacing bands.

In any event, re its' accuracy, when I check it against Naval Observatory/NIST Time, a 2 person job the way I do it, one calling "mark" respecting the dynamic time tic, the other reading the watch, no differece is detrected, which I take to indicate that the Casio watch is dead on.

As to price, that may have changed over several years, but when I bought the thing on Amazon.com, I paid $50-55, shipped free.

I don't think that such navigation problems as I have had, shooting the sun, moon, planets or stars standing on the beach have involved errors in time. Actual sextant shots, and hitting the wrong key on my calculator, and or transposing numbers read from the NA are a whole different story though, the possibilities of "operator error" being endless.
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