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Lesson 15: Voyage Planning and Time

Lesson 15: Voyage Planning and Time. 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. Terms and Definitions.

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Lesson 15: Voyage Planning and Time

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  1. Lesson 15: Voyage Planning and Time

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  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.

  9. Determining the Time Zone • To determine the time zone, simply divide the longitude of a location by 15. • If the remainder is < 7 1/2°, quotient is the zone • If the remainder is > 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.

  10. 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 1°18’ • 1°18’ < 7°30’  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

  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 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

  13. Time Conversion Example • It’s 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

  14. 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

  15. Shipboard Time • During a transit, the ship’s 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.

  16. 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

  17. 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  

  18. 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.

  19. Optimum Track Ship Routing (OTSR) OTSR Provides: • Preliminary planning • Route Recommendations • Route Surveillance • Divert Recommendations

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

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