Lesson 14: Voyage Planning and Time

1
Lesson 14 Voyage Planning and Time
2
Lesson 14 Voyage Planning and Time

• Learning Objectives
• ETA/ETD
• Determine Zone Time for specific locations
• Convert longitude into equivalent time units
• Date-time Group (DTG) Format
• Planning an Extended Ocean Voyage
• Plotting a Great Circle Route
• OTSR
• PIM

3
Time Terminology

• Estimated Time of Arrival (ETA) the time and
  date of arrival that must be achieved. Usually
  specified by higher authority.
• Estimated Time of Departure (ETD) a computed
  estimate of the time and date of departure that
  will allow the ship to arrive on time.

4
The Mean Sun Zone Time

• The rate at which the sun moves across the sky
  varies day to day due to the earths elliptic
  orbit about the sun.
• This makes use of actual time rather difficult.
• Instead, the theoretical mean sun, which passes
  completely around the earth once each 24 hours,
  is used to measure time.

5
The Mean Sun Zone Time

• The mean sun completes one circuit around the
  earth every 24 hours, or 15 degrees of longitude
  each hour.
• Each 15 degrees of arc is a time zone.
• Within each zone, time is reckoned according to
  the position of the mean sun in relation to the
  central meridian of the zone.

6
Greenwich Mean Time (GMT)

• Centered on prime meridian.
• Extends 7.5o east and west of the prime meridian.
• Referred to as zulu time, because the time zone
  is designated by Z.
• Each additional time zone (as we move east or
  west) has a boundary every 15 degrees past 7.5o.

7
Figure 15-1 in Hobbs (page 254)
8
The International Date Line

• The 24th time zone is split in half, with each
  zone on either side of the 180th meridian being
  only 7.5o wide.
• To remember what day it is on each side of the
  line, the phrase San Francisco to Manila, Sunday
  to Monday is used

9
Determining the Time Zone

• To determine the time zone, simply divide the
  longitude of a location by 15.
• After this is done, round to the nearest whole
  number.
• For eastern longitudes, place a negative sign (-)
  in front of the number for western longitudes,
  place a positive sign () in front of the number.

10
Time Zone Example

• The longitude of Norfolk, Virginia is 076o 18.0
  W. What time zone is this?
• Answer
• 076o 18.0 076.3o
• 076.3/15 5.09, or rounded to the nearest whole
  number, 5.
• Since longitude is west, time zone is 5.
• The time zone indicator letter for this zone is
  R, so the zone is completely described as 5R

11
Daylight Savings Time

• As an example, when Norfolk observes daylight
  savings time, it keeps 4Q instead of 5R time.
• The time kept at any particular location and time
  of the year can be determined from either Coast
  Pilots or Sailing Directions.

12
Time Conversions

• During voyage planning, all times are normally
  expressed in terms of GMT to avoid confusion.
• As necessary, times are converted to the local
  time zone for ease of use.
• ZTZone Time (time at current location)
• ZDZone Difference or Description (difference
  between GMT and ZT)
• ZTZDGMT (converting zone to GMT)
• ZTGMT-ZD (converting GMT to zone)

13
Time Conversion Example

• Its 0800 (local zone time) in Naples, Italy.
  What is this time, expressed as GMT?
• Answer
• Longitude of Naples is 14o 16 E, so the time
  zone is -1A.
• GMT ZT ZD 0800 - 1 hour 0700 Z

14
Time Zone Conversions

• Note that the date may change as a result of the
  time zone conversion.
• For example if it is 0030A 30 June in Naples,
  this translates to 2330Z 29 June.

15
Date Time Group (DTG)

• Official Navy format for expressing time and
  date. Also in all naval message traffic.
• An example 101300SMAR06 translates to
• 10 1300 S MAR 06
• DAY 4-DIGIT TIME 3 LETTER LAST TWO
• OF TIME ZONE MONTH DIGITS OF YEAR
• MONTH INDICATOR

16
Shipboard Time

• During a transit, the ships clocks are set to
  the time zone in which the ship is located.
• As the ship transits eastward, clocks are
  periodically advanced 1 hour to conform to the
  proper time zone, and vice versa for westward
  travel.

17
The Voyage Planning Process

• Obtaining and updating charts and publications.
• Determination of arrival and departure dates and
  times.
• Plotting the intended track and use of Optimum
  Track Ship Routing (OTSR).

18
Optimum Track Ship Routing (OTSR)

• OTSR is a forecasting service provided by the
  Naval Oceanographic Command to vessels making
  transoceanic voyages.
• Preliminary planning
• Route Recommendations
• Route Surveillance
• Divert Recommendations

19
Plotting the Intended Track

• Consult all available publications (including
  Sailing Direction Planning Guides, Coast Pilot,
  Distance Between Ports)
• Plot track on gnomonic chart to get great circle
  track
• Pick convenient points every 300-500 miles to
  transfer to a mercator chart
• Transfer these points to smaller scale/larger
  area charts for day-to-day use

20
(No Transcript)
21
(No Transcript)
22
PIM

• Position of intended movement (PIM) The
  theoretical position of the ship on the intended
  track at any time. The PIM moves along the track
  at the SOA, and the actual ships position can be
  described in relation to it. If the ship arrives
  two hours ahead of the planned ETA at point C,
  for example, it is said that the ship is two
  hours ahead of PIM at that point.
• PIM points are plotted in GMT, typically every
  four hours
• Hobbs pg 267

23
(No Transcript)
24
Homework

• Read Chapter 16, Skim CH 17-18
• Chapter 15
• Section 1 4-12
• Section 2 5-7
• Quiz Tuesday over Lessons 10-13