# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Digital watches as chronometers**

**From:**Gary LaPook

**Date:**2020 Oct 28, 01:37 -0700

This is another update on my experiment using three cheap, $17.00,

watches as a chronometer.

I obtained another set of data today, October 28, 2020 Z at

0602 Z, 4058 days since the start, more than ELEVEN YEARS

See attached photo taken at 06:02:28Z,

watch "A" is 16 minutes and 42 seconds fast, etc. (The seconds

are in the top windows.)

I have not had to replace any of the batteries in ELEVEN YEARS.

At the beginning of this experiment I determined the daily rate of

each watch from a 99 day sample. Watch "A" has a rate

of 0.1919 seconds fast per day; watch "B", 0.3737 fast; and watch

"C" is 0.6263 fast. Using these values I calculated what the

predicted corrections would be, the values that would be

used by the navigator to correct the chronometer time,

and compared with the measured values.

The differences show how much of a navigational error would have

resulted from the navigator using the predicted times.

In the format for A, B, and C in seconds: actual error;

predicted error; difference.

A = 1002/825/177 fast: B = 1483/1539/56 slow: C = 2569/2601/32 slow

Averaging these differences equals 30 seconds fast.

Using only one watch with the largest error, 177 seconds, would

resulted in a 44 minute of longitude error. Using the average of

all three watches would have produced an error of only 7.4 minutes

of longitude, not bad for fifty-one dollars worth of watches

after more than ELEVEN YEARS.

============================================

Prior update:

This is another update on my experiment using three cheap, $17.00,

watches as a chronometer.

I obtained another set of data today, May 31, 2013 Z at

0108 Z, 1351 days since the start, more than three years

and eight months. See attached photo taken at 01:08:00Z,

(WWV radio signal)

watch "A" is 5 minutes and 6 seconds fast, etc. (The seconds

are in the top windows.)

I have not had to replace any of the batteries.

At the beginning of this experiment I determined the daily rate of each watch from a 99 day sample. Watch "A" has a rate of 0.1919 seconds fast per day; watch "B", 0.3737 fast; and watch "C" is 0.6263 fast. Using these values I calculated what the predicted corrections would be, the values that would be used by the navigator to correct the chronometer time, and compared with the measured values. The differences show how much of a navigational error would have resulted from the navigator using the predicted times.

In the format for A, B, and C in seconds: actual error;

predicted error; difference.

A = 306/266/+40 fast: B = 528/536/ -8 slow: C = 906/846/-20 slow

Averaging these differences equals 4 seconds fast.

Using only one watch with the largest error, 40 seconds, would

resulted in a 10 minute of longitude error. Using the average of

all three watches would have produced an error of only one minute

of longitude, not bad for fifty-one dollars worth of watches

after more than three and a half years.

See my prior reports at:

http://fer3.com/arc/m2.aspx/Watches-chronometers-LaPook-oct-2011-g17175