Sea Time

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Sea Time
Homework Q A

• Junior Navigation
• Chapter 3

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Objectives Determine watch error and rate.
Obtain an accurate time check by radio time
signals. Determine zone description from
longitude. Find the zone description for
standard time zones ashore. Determine Universal
Time (UT) for sights Convert zone time (ZT) to
Universal Time (UT). Convert Universal Time
(UT) to zone time (ZT). Convert one ZT to a
second ZT. Allow for travel time or other
intervals in zone time conversions. Describe the
principles of timekeeping at sea. Draw a time
diagram to visualize longitude, UT, and ZT.
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Practical Exercises Problems 1 through
2 Follow the Student Manual for guidance
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3. On 2 March, a watch reads 22-30-56 at the
instant a 2230 time signal is received. On 4
March at the 2230 signal, it reads 22-30-55 and
on 6 March, it reads 22-30-54. What is the rate
of this watch?
a. 1 second per day slow.b. 0.5 second per day
fast.c. 2 seconds per day slow.d. 0.5 second
per day slow.
Watch has lost 2 seconds in 4 days, so rate is
slow 0.5 second per day.
REF 6-8
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4. To determine the rate of a timepiece, compare
the timepiece to a
a. radio time signal at 12-hour intervals
for 3 days.b. radio time signal at 24-hour
intervals for 1 week.c. radio time signal on one
day at 2- hour intervals at least 6 times.d.
commercial radio time announcement at hourly
intervals for a full day.
REF 7
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5. WWV /WWVH stations broadcast on

• a. 16.25,16.5,16.75, and 17.0 MHz.
• b. 2.5, 5.0, 10.0, 15.0, and 20.0 MHz.
• c. 2.5,5.0, 10.0, 15.0, and 20.0 KHz.
• d. 3.30,7.335, and 14.670 MHz.

REF 12
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6. The effect of Daylight Saving Time on the
observer's zone description (ZD) in western
longitudes is
a. to add 1 to its value.b. to subtract 1 from
its value.c. negligible.d. not determinable.
REF 31
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7. Using a current Almanac, find the zone
descriptions for the following places on 15
March
List III ZD4 List I ZD-12 List II ZD0 ZD -6 hr
30 min
a. Halifax, Nova Scotiab. Auckland, New
Zealandc. Reykjavik, Icelandd. Rangoon, Burma
Ref. Nautical Almanac Standard Time Tables
beginning on page 262
REF 25
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8. Zone Description (ZD) is
a. always positive in east longitude. b. the
longitude of the zone meridian divided by
15 rounded to a whole number, with a
plus or minus sign (depending on if W or E
longitude). c. the difference between Universal
time and local time, expressed to the
nearest hour. d. the difference between zone
time and local time, expressed to the
nearest hour.
REF 28
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9. ZT 0000 occurs at your zone meridian when
a. the apparent sun is overhead.b. the
apparent sun is on the horizon.c. the mean sun
is 180 from the upper branch of the zone
meridian. d. the mean sun is at the upper
branch of the zone meridian.
REF 34
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10. In the time diagram shown in Figure 3-13
(below) a. What is the observer's
longitude?b. What is his ZT?c. What is UT?
Lo 135E
ZT 0400
UT is 1900 the previous day
a. From Time Diagram in Fig. 3-13, Lo is 9 hrs.
east of G and Lo 9 x 15 Lo 135E.
Figure 3-13
c. The Sun is 75/(15/hr) 5 hr before g, so
UT 2400 - 0500 1900 the previous day.
REF 36, 37
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11. You take a sextant observation and record the
time of the your observation. What time do you
use to enter the Nautical Almanac?
a. local standard time throughout the yearb.
local daylight time when applicable
otherwise, local standard time c. Universal
Time (UT)d. Universal Time (UT) adjusted for
Daylight Saving Time if applicable
REF 38
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12. For each of the following longitudes, find
the zone description (ZD).
ZD 9 ZD -3 ZD 0 ZD 0

1. Lo 137 14.5'W
2. Lo 42 55.5 'E
3. Lo 7 29.2 'W
4. Lo 7 29.2'E

a. Solution (137 (14.5' / 60)) / 15
9.149ZD 9
b. Solution -(42 (55.5' / 60)) / 15 -2.86
ZD -3
c. Solution (7 (29.2' / 60)) / 15 0.49911
ZD 0
d. Solution -(7 (29.2' / 60)) / 15 0.49911
ZD 0
REF 39 - 43
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13. For each of the following zone times, find
UT.
a. Zone time is 1000 in zone 6 Ans 1600
UT b. Zone time is 1800 in zone -6 Ans
1200 UT c. Zone time is 1600 in zone 9
Ans 0100 UT next day d. Zone time is 2000
in zone -12 Ans 0800 UT
REF 45 - 52
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14. For each of the following UT, find the
corresponding zone time. a. UT is 1800, Lo is
75W Ans 1300 ZT, ZD75/155 b. UT is
1800, Lo is 75 E Ans 2300 ZT, ZD75/15-5
c. UT is 1000, Lo is 135 W Ans 0100 ZT,
ZD135/159 d. UT is 1000, Lo is 135 E
Ans 1900 ZT, ZD135/15-9
REF 54 - 56
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15. You are fishing in the Galapagos Islands and
have arranged to make radio contact daily at 1630
(their time) with Guayaquil, which keeps zone 5
time. You keep zone 6 time aboard.What is the
ship's time of the radio contact?
Ans ZT 1530, ship's clock time
SolutionZT1 1630 Guayaquil time of planned
contact ZD1 5 Guayaquil ZD UT 2130 ZD2 6
(rev) Vessel time ZD ZT2 1530 Local time of
call (same day)
REF 59 - 64
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16. You are in Chicago and wish to speak to a
business associate in London, England. He can be
reached by telephone only at 830 A.M., London
time. What will the time be in Chicago when
you make your call?
Ans ZT 0230, same day, in Chicago
Solution ZT1 0830 London time of planned
contact ZD1 0 London ZDUT 0830 ZD2 6
(rev) Chicago ZDZT2 0230 Chicago time of
call (same day)
REF 59 - 64
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17. On 24 December, a vessel bound eastward at 10
knots for the Hawaiian Islands expects to cross
the International Date Line at midnight (ZT prior
to the crossing). How many hours thereafter
will plum pudding be served at noon, Christmas
Day?
Ans 36 hrs will elapse
Solution When crossing the IDL in an easterly
direction, you are going from east Lo to west Lo,
and you will 'lose' a day. ZT1 2400 24 Dec
ZT date before crossing IDLZD1 -12 ZD
before crossingUT 1200 24 DecZD2 -12
(rev) ZD after crossingZT2 0000 24 Dec ZT
date after crossingZT3 1200 25 Dec ZT2 -0000
24 Dec ET 12 hr 1 day 36 hours
REF 69 - 72
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18. The vessel's log and plot should be kept
according to
a. zone time.b. ship's time.c. Universal
Time.d. Daylight Saving Time.
REF 78
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19. Find UT and date for the following      
Watch Time WE ZD Date a. 07-27-14 f
1-14 -8 12 Mar    b. 19-27-14 s 1-14
8 12 Mar    c. 11-52-28 s 1-46 -6 23
Aug    d. 20-02-32 0-00 5 30 Mar
UT Date 23-26-00 11 Mar 03-28-28
13 Mar 05-54-14 23 Aug 01-02-32 31 Mar
REF 49 - 52
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Sea Time
End of Homework Q A

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