Lesson 15: Voyage Planning and Time

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Lesson 15 Voyage Planning and Time
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Lesson 15 Voyage Planning and Time

• AGENDA
• ETA/ETD
• Determining Zone Time
• Date-time Group (DTG) Format
• The Voyage Planning Process
• Optimum Track Ship Routing (OTSR)
• Applicable reading Hobbs pg. 252-274.

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Terms and Definitions

• 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.

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Terms and Definitions

• Speed of Advance (SOA) The speed intended to
  be made good along the track.
• The average speed in knots which must be
  maintained during a passage to arrive at a
  destination at an appointed time.

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Terms and Definitions
PIM-

• Planned track movement based on required SOA
• USS Indianapolis
• Indicated every 4 hours
• Needed for ALL Voyage Plans
• PIM symbol must be different from standard
  navigation symbols. Ex

1200Z PIM
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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.

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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.

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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.

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Determining the Time Zone

• To determine the time zone, simply divide the
  longitude of a location by 15.
• If the remainder is lt 7 1/2, quotient is the
  zone
• If the remainder is gt 7 1/2, shift to the next
  zone
• For eastern longitudes, place a negative sign (-)
  in front of the number for western longitudes,
  place a positive sign () in front of the number.

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Time Zone Example

• The longitude of Norfolk, Virginia is 076o 18.0
  W. What time zone is this?
• Answer
• 076 18.0/15 5 w/remainder of 118
• 118 lt 730 ? Zone description 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

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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.

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Time Conversions

• During voyage planning, all times are normally
  expressed in Zulu (GMT) to avoid confusion.
• As necessary, times are converted to the local
  time zone for ease of use.
• The formula for all conversions is
• Zone time zone description GMT

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Time Conversion Example

• Its 0800 (local zone time) in Naples, Italy.
  What is this time, expressed as GMT?
• Answer
• Longitude of Naples is 014o 16 E, so the time
  zone is -1A.
• GMT ZT ZD 0800 - 1 hour 0700 Z

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Date Time Group (DTG)

• Official Navy format for expressing time and
  date. Also in all naval message traffic.
• An example 171000RJUN89 translates to
• 17 1000 R JUN 89
• DAY 4-DIGIT TIME 3 LETTER LAST TWO
• OF TIME ZONE MONTH DIGITS OF YEAR
• MONTH INDICATOR

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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.

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Rhumbline Track on Mercator Chart

• Rhumbline Sailing
• Appears As a More Direct Route on Mercator
  Projection
• Maintains Constant True Direction and the Same
  Angle at All Longitude Meridians
• For Short Distance Tracks
• Rhumbline Is Same As GC Track

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Track Development

• Steps
• Select Great Circle and Mercator Charts
• Depart and Destination Positions Plotted
• Start at First 5 Long Meridian Retrieve
  Latitude and Longitude every 5 Meridian
  thereafter ?
• Transfer Track Positions to Mercator Projection
• Record Positions on PIM Sheet ?

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The Voyage Planning Process

• Obtain and update charts and pubs
• Determine time of arrival and departure.
• Plot the intended track
• Plot a great circle on a gnomonic projection
• Transfer rhumb lines to a mercator projection
• Construct a track summary listing courses,
  distances, and times for each leg.

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Optimum Track Ship Routing (OTSR)

• OTSR Provides
• Preliminary planning
• Route Recommendations
• Route Surveillance
• Divert Recommendations

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REVIEW

• What is SOA?
• What is OTSR?
• ZULU time is also known as _______?
• What time zone is Voyage Planning completed in?