16-Voyage Planing and Time

5/24/2018 16-Voyage Planing and Time

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Lesson 15: Voyage Planningand Time

Learning Objectives: Apply correct procedures to

determine zone time for specificlocations.

Apply correct procedures todetermine zone time at anotherlocation if zone time is known at agiven location.


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Comprehend the process ofplanning for an extended oceanvoyage, and the services andpublications that can be of

assistance during voyage planning.


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At the beginning time was easy


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There was only

the sun and the man


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Some ti

me later someone inventedthe clock


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Different cities had differenttimes


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The problem started when someoneinvented the train

Close towns need to have the same time


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We said the problem startedbecause:

Towns close to each other need to havethe same time

And towns far apart need to havedifferent times


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SO SOMEONE INVENTED THETIME ZONES

They said: the day has 24 hours.


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He said: the day has 24 hours. The sun appears to make a complete path

(360) around the earth in one day


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He said: the day has 24 hours. The sun appears to make a complete path

(360) around the earth in one day

So if we divide 360 by 24 the result will be 15

sun moves at a rate of 15 degrees arc measuredeither at equator or position of longitude every hour


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15

15 = one hour

360

24


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15

360, one turn = 24 hours, one day

360


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Time Zones

360 degreessplit up into

24 time

zones whichequals 15

degrees of

longitudeper time

zone.


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15= 1 hour


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Timewhy is it important invoyage planning???

ETA assigned by higher authority

ETD

Nav solves based on ETA Time Zones

15 degrees of longitude

Referenced to time zone with PrimeMeridian at center.


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Greenwich Mean Time (ZULU) - time in relationshipwith mean sun and prime meridian

GMT Zone is centered on Prime Meridian(000 degrees longitude) and extends +/-7.5 degrees on each side of the PrimeMeridian

zones west (+) of GMT

earlier time zones than GMT add hourly time difference to local time to obtain Zulu

time

zones east (-) of GMT later time zones than GMT

subtract hourly time difference to local time to obtainZulu time


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22.5 15 7.5 0 7.5 15 22.5

W E

Zone Zone Zone

+ 1 N 0 Z -1 A

Time Zones


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Time Zones

Zone Description 24 time zones based on GMT

+1 to +12

-1 to12

In reality, including GMT, there are25 time zones

ZD = Labeled with letter and numberindicator

Example: ZD of Norfolk, VA is +5R


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Equator


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Equator

- - - - - - - - - - -

X W V U T S R Q P O N Z A B C D E F G H I K L

11 10 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11

+ + + + + + + + + + +

+12 Y-12 M


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Time Zones To calculate the Zone Description for a given

position, complete the following steps inorder:

Divide longitude of position by 15 to getcenter of time zone

if remainder less than 7.5, the quotientrepresents the zone

if remainder greater than 7.5, location is nextzone away

if no remainder, location lies in central meridianof zone

Example: 062 degrees West

062/15 = 4 with a remainder of 2 ZD = +4

Example: 072 degrees West

072/15 = 4 with a remainder of 8

ZD = +5


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Time Zones

Time Conversions - Navigator will convertall times to GMT for planning process

Convert ETA, ETD to GMT

ZT+ZD=GMT

ZT=GMT-ZD

Label time = Date Time Group

091800 Z OCT98

Two digit day/24-hr time/ZD letter indicator/3 letter month/last two digits year


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Example of Time ConversionProblems

Convert the following local zone timesto GMT(Zulu) times:

1000R 15 November 1997

ZT+ZD=GMT

151000 R NOV97

+5R

151500 Z NOV97

*Use Figure 15-1 to assist with ZD

f C


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Example of Time ConversionProblems It is 0750 on 20 November in Norfolk, VA

(approx. 073 degrees West). What time is it inOman (approx. 042 degrees East)?

1. Convert Norfolk time to Zulu:

200750 R NOV

+5R______

201250 Z NOV

2. ZT = GMTZD (for Oman)

= 201250Z NOV

- (-3C)_____

201550 C NOV

Vo age Planning


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Voyage Planningand Time

Time - Time is of major importance in every voyage planning process; almost everyplanning action is concerned with the timely arrival at the ultimate destination and at

intermediate points en route. Estimated time of arrival (ETA): The time and date of arrival that must be met.

They are usually specified by higher authority.

Estimated time of departure (ETD): A computed estimate of the time and date ofdeparture that will allow the ship to arrive on time. The ETAs at several pointsalong the track must also be computed in order to check progress .

Development of Zone Time - The rate at which the sun moves across the skyvaries from day to day due to the earths elliptic path around the sun. To avoid

difficulties that arise from this fact, the concept of a theoretical mean sunpassing completely around the earth at the equator once every 24 hours has beenadopted.

The Mean sun completes one circuit around the earth every 24 hours and movesat the rate of 15 degrees of longitude every hour.

Time zones: Vertical sectors that divide the earths surface into twenty fourzones. Each zone is 15 degrees of longitude in width (15*24=360 degrees).

Zone time (ZT): Time within each zone is reckoned according to the position of the

mean sun in relation to the central meridian of the zone. Clocks are changed by one hour increments when transiting from one 15 degree

zone to another.


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Each time zone is defined by the number of hours of differenceexisting between the time kept in that zone and the time kept withinthe zone centered on the prime meridian.

Time zone indicators: Each zone is labeled with a letters thatassists in identification of the zone.

Greenwich Mean Time (GMT): Time based upon the relationship of themean sun with the prime meridian. It is often referred to as ZULU time,because of its time zone indicator letter.

Times zones to the west of Greenwich keep earlier time in relationto GMT. This is indicated by placing a plus sign in front of thehourly difference figure to indicate the number of hours that mustbe added to the local zone time to convert it to GMT.

Times zones to the east of Greenwich keep later time relative toGMT. This fact is indicated by placing a minus sign in front of thehourly difference. This gives the number of hours that must be

subtracted from local zone time to obtain GMT. The Greenwich Time Zone is centered at the prime meridian, and

extends 7 1/2 degrees to either side. A new time zone boundary liesevery 15 degrees thereafter across both the eastern and westernhemispheres, resulting in the twenty fourth time zone being splitinto two halves by the 180th meridian. The half on the west side ofthis meridian keeps time 12 hours behind GMT making its

difference +12 hours. The half on the east keeps time 12 hours


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ahead, resulting in a difference of -12 hours.

Zone difference or zone description( ZD): There are actually25 different time zones , numbered from +1 through +12 to thewest of the Greenwich time zone, and -1 through -12 to theeast. These differences are known as zone differences.

The standard time zone in which any particular position on earth islocated can be found by dividing its longitude by 15.

If the remainder is less than 7 1/2 degrees, the quotient

represents the number of the zone; if the remainder is greaterthan 7 1/2 degrees, the location is the next zone away from theGreenwich Meridian.

Example: Determine the standard time zone of Norfolk,Virginia. Its longitude, 076o18.0 West, is divided by 15 to yielda quotient of 5 with a remainder of 1o 18. Thus, it is located inthe +5 time zone, which has the time zone indicator letter R.

15 degree time zones are of use to a navigator at sea, but strictadherence to these time zones is not practical for conductingbusiness and travel. Consequently, time zones are oftendrawn along state and county boundaries.



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Daylight savings time is a device adopted by some countries, including the UnitedStates, to extend the hours of daylight during the summer. Locations keeping

daylight savings time keep the time of the next zone to the east of the time zone inwhich they are located.

Example: When Norfolk observes daylight savings time, it keeps +4Q timerather than +5R time.

The time kept at any particular location and time of year can normally be foundin the applicable volume of the Sail ing Direct ionsfor foreign ports or the CoastPi lots for U.S. ports.

Time conversions- All times are converted to GMT prior to the initial planning

stages of the voyage to avoid the difficulties inherent in working with severaldifferent time zones. After all ETAs and ETDs have been computed in GMT, certaintimes of interest can then be converted to local time zones.

The following formulas are used to convert zone time to GMT and GMT to zonetime: ZT+ZD=GMT (converting zone to GMT)

ZT=GMT-ZD (converting GMT to zone)

Example: Convert 0800 local zone time on 30 June at Naples, Italy toGreenwich Mean Time. The longitude of Naples is 14o16 East, so it lies in the -1A time zone. The local time to be converted is written 0800A 30 June. Thezone difference is applied to this time giving GMT of 0700Z 30 June.



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Note: The date may change as a result of the conversion process.For example, converting 0030A 30 June to GMT would yield a

computed time of 2330Z 29 June. Date-time group: an alphanumeric format used in labeling the track,

as well as in writing messages. An example is shown below:

1 7 1 0 0 0 R J U N 8 9DAY 4-DIGIT TIME 3 LETTER LAST

OF TIME ZONE MONTH TWO

MONTH INDICATOR ABB DIGITS

OF YEAR

During a transit, the ships clocks are set to the time zone in whichthe ship is located.

When transiting in an easterly direction, ships clocks will beperiodically set ahead 1 hour to conform to proper time zone.

When traveling in a westerly direction, clocks will beperiodically set back to conform.

The 180th meridian is designated as the International Date Line,because the time kept in the 7 1/2o -wide zones on either side of itdiffers by 24 hours, or one complete day.

When crossing the dateline on a westerly heading, the zonedescription changes from +12 to -12. Clocks must be advanced24 hours, thereby losing one calendar day.

When crossing in an easterly direction, clocks are retarded 24hours, thereby gaining one calendar day.


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The voyage planning process: In the case of Navy ships, the firstnotification of a deployment and its associated transits is normallyreceived via the Yearly Employment Schedule. Confirmed deploymentdates or changes to a ships schedule will be reflected in QuarterlyEmployment Schedules. Navigators must take into account numerouspublication/chart, equipment, personnel, and operational chartconsiderations when beginning the planning process:

Obtaining and updating charts and publications:

The navigator will consult applicable chart allowance lists inorder to determine which charts should be in the ships inventory.Any outdated or missing charts are ordered from the DefenseMapping Agency or National Ocean Service.

The navigator will also consult the DMA Catalog of Maps, Chartsand Related Publ icat ions and the NOS Nautical Chart Catalog 1tofind the numbers of all charts and Coast Pi lots and Sail ing

Direct ions volumes that will be of use in the voyage. The Chart Petty Officer will pull all applicable charts and their

correction cards and update all information.

Determination of departure and arrival dates:

Regardless of whether a ship will transit independently or incompany with other ships, an ETA (estimated time of arrival) willbe promulgated by a higher authority. It is up to the navigator tocalculate an estimated


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time of departure that will allow the ship to arrive at the assigned time.

Example: A ship will transit from Norfolk to Naples, Italy with an ETA OF 0800A

30 June. First: Determine the distance between Norfolk and Naples usingPublic at ion No. 151, Distanc e Between Ports.A great circle route can besailed from Norfolk to Gibraltar (3,335 miles), then from Gibraltar toMessina (1.049 miles), and finally from Messina to Naples (175 miles).Adding the three together yields a total distance of 4,559 miles. MaximumSOA (speed of advance) will be promulgated by higher authority; for thisexample a maximum SOA of 16 kts is assumed. Using the speed-time-distance equation, a total time in transit of 285 hours, or 11 days and 21

hours is obtained. Second: Norfolk is in time zone +5R while Naples is located in time zone -

1A. Consequently, 6 hours will be lost due to time zone changes duringthe transit. The ship must depart Norfolk 12 days and 3 hours before thescheduled arrival in Naples. Subtracting this time from the ETA of 0800A30 June yields a departure time from Norfolk of 0500R 18 June. Analternative method would be to convert the ETA to GMT, subtract 285hours, then convert this GMT time to +5R for Norfolk.

Tides and currents must be taken into account when determining ETD and

ETA as the calculated underway and arrival


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times may need to be adjusted to compensate for these factors.

Plotting the intended track:

The navigator will consult a climatologically summary provided by theNational Oceanography Command Center, in order to account for prevailingweather for the period of the transit. This survey provides normal windspeeds and directions, wave heights, currents, and the probability of rain andstorms enroute. Other sources of this type of information are the appropriateeditions of Sail ing Direct ions Planning Guides, and Coast Pi lots.

Consulting these references ensures that the optimum route is chosen

for the voyage. It is possible that heavy weather could slow a ship alonga great circle route, and that a longer track may save time by avoidingbad weather.

An Optimum Track Shipping Routing will also be requested from theNational Oceanography Center. This track is an optimum track for thespecific ship requesting the service based on actual climatological andhydrographic forecasts covering the time of the voyage.

Once the OTSR is received, it will be compared to the track proposed by

the navigator. The track may be altered to adjust for bad weatheridentified by the OTSR.


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After determining the optimum track, the navigator will plot the trackon a gnomonic chart.

The great circle track obtained from this plot is then transferred onto amercator chart by picking convenient points every 300 to 500 milesapart and plotting them on the mercator projection (see App. A).

These points are labeled either with letters or sequential alphanumericdesignation such as R-1, R-2 etc. These points are then connectedwith rhumb lines.

Since the area covered by the chart depicting the North Atlantic is solarge and the scale so small, the points on the track are also plotted onlarger scale, smaller area charts for day-to-day use.

Completing the Track:

After the track from point A off Hampton Roads to the entrance to Napleshas been laid down, the exit track from Norfolk and the entrance track toNaples are both plotted on the appropriate charts.

The navigator then measures the distance along the rhumb line tracks andcompares the total to the distance obtained from Public at ion No. 151,Distanc e Between Ports. After computing the speed of advance for eachleg, each junction point on the large-scale chart is labeled with the distance

remaining to the


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destination and the computed ETA at each point, expressed in bothGMT and local time zone. As a minimum, each rhumb linesegment on the large-scale plot should be labeled with the trackdirection and speed of advance, and each junction point should belabeled with the distance remaining and the ETA in local time zone.

--Position of intended movement (PIM): The theoretical position ofthe ship on the intended track at any time. The PIM moves alongthe track at the SOA, and the actual ships position can bedescribed in relation to it. If the ship arrives two hours ahead ofthe planned ETA at point C, for example, it is said that the ship istwo hours ahead of PIM at that point.



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Misc. Considerations

Ships position log - Navy directives require that legal

document be maintained when ship is underway

located on Bridge and CIC

fixes recorded with accompanying depth soundings,intermediate DR positions, and set/drift of current

Ships position report - formal report from Navigator to

Commanding Officer of position of ship at 0800, 1200, and2000 when ship is underway

standard format

distance to/ETA at next track junction point

amount of time ship ahead/behind intended track

MOVREP - several days prior to underway ship submitsmovement report

informs impending departure of ship

detailed description of every waypoint in planned track

ETA

SHIP REQUIRED TO STAY W/N +/- 4 HOURS OR +/- 50 NMOF PIM - UPDATE MOVEREP IF NOT


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LOGREQ - sent several days prior to entering port

ships arrival/departure dates/times

any services or logistic support required

Captains Night Orders -

drafted by Navigator and signed by Commanding

Officer supplementary instructions of activities each watch

is to carry out at night


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Voyage Planning

Voyage Plan problem: Need to be in AugustaBay, Crete by 1600 (-1A) on the 17th ofSeptember. Its 5085 miles from Norfolk.Youre authorized 16 kts. When do youleave?


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Example

Step 1: 5085 miles divide by 16 kts.

It will take 318 hours to get from Norfolk toAugusta Bay at 16 kts.


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Example

Step 2: Convert ETA to Z time. 1600 (-1A) is 1500 Z


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Example

Step 3: Divide 318 by 24. 13 days

remainder of 6 hours


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Example

Subtract 13 days 6 hours from ETA

1500 Z 17 Sept

0600 13

ETD: 0900Z 04 Sept

transfer to local time = +5R

ETD: 0400R 04 Sept


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Voyage Planning problems:

A ship leaves Norfolk, VA at 061030 R OCT and arrives at

Cape Town, South Africa (approx. 20 degrees East) at 161545A OCT. For how many days, hours, and minutes was the shipunderway??

Step 1: convert all times to Zulu

Step 2: subtract the times

061030 R OCT 161545 A OCT

+5R -1A

061530 Z OCT 161445 Z OCT

16 14 45 Z OCT

-06 15 30 Z OCT

09days 23hrs 15min


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Homework

Workbook Chapter 15

Section 1: Time

49

Read Weather chapter in your workbook (Appendix ABasic Meteorology)

25 OCTExam Review (Read Chapters 16-19) Celestial ppt. On web. = pay attention to basics of

each coordinate system

30 OCTExam #2

Documents

16-Voyage Planing and Time