Maritime Economics SA Grade 11

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    International time zones and the international date line

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    • Grade 11 – Maritime Economics
    • 11.1 The Maritime World 11.1.3 International Time Zones & International Date Line
    • International time zones and the international date line
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    August 31, 2016
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    To revise the main facts in this section, go to the section in the Grade 10 site.

    Remember the following from that section :

    • For every 15˚ of longitude, the sun time changes by 1 hour.
    • Port A (to the east of Port B) will be ahead of Port B in time.
    • Port C (to the west of Port D) will be behind Port D in time.
    • A ship crossing the International Date Line from east to west (e.g. from the Pacific coast of Canada to China) will advance her clocks 24 hours of time.
    • A ship crossing the International Date Line from west to east (e.g. from New Zealand to Panama Canal) will subtract (miss) 24 hours of time.

     

    Calculating the Expected Time of Arrival (ETA) of a ship

     

    Example A: What is the ETA of the ship in Port Y at Port Y’s time?

    Given facts :
    Port of Departure Port X (15˚W)
    Time of Departure 10:00 on 3 June
    Port of Destination Port Y (135˚E)
    Distance to be steamed  5040 Nautical Miles
    Average Speed  15 knots

    11.1.3_Voyage_calculations_1

    But this time of arrival at Port Y is 10:00 on 17 June at Port X’s time.

    We need to convert this to ETA the local time at Port Y.

    11.1.3_Voyage_calculations_2

     

    Example B: What is the ETA of the ship in Port Q at Port Q’s time?

    Given facts :
    Port of Departure Port P (45˚E)
    Time of Departure 07:00 on 15 August
    Port of Destination Port Q (120˚W)
    Distance to be steamed 5184 Nautical Miles
    Average Speed 18 knots

    11.1.3_Voyage_calculations_3

    But this time of arrival at Port Q is 07:00 on 27 August at Port P’s time.

    We need to convert this ETA to the local time at Port Q.

    11.1.3_Voyage_calculations_4

     

    Example C:

    This is an interesting example because it includes actual ports, actual distance and a ship crossing of the International Date Line while steaming between those ports.

    Given facts :
    Port of Departure Valparaiso, Chile (Takes its time from 60oW)
    Time of Departure 09:30 on 25 May
    Port of Destination Sydney, Australia (Takes its time from 150oE)
    Distance to be steamed  6281 Nautical Miles
    Average Speed 20 knots

    Let’s go to www.sea–distances.org and follow the steps below.

    Click Voyage Calculator.

    Click Add Port.

    Go to the box, select Chile and then select Valparaiso.

    Click Add Port.

    Go to the box, select Australia and then select Sydney.

    Enter also the speed (20 knots).

    Now change the ETD from Valparaiso to 0930 on 25 May.

    A calculation will be done automatically.

    Now note how many days it will take to steam from Valparaiso to Sydney.

    Note also the ETA at Sydney.

    BUT the calculation has not taken into account the fact that the ship has crossed the International Date Line from east to west. This means that we need to advance the time by 24 hours, i.e. add 24 hours to the given ETA at Sydney.

    Modules

    • 11 Introduction
    • 11.1 The Maritime World
      • 11.1.1 Lloyd’s Register of Shipping
      • 11.1.2 Trade routes and port locations
        • 11.1.2.1 Southern African Ports
        • 11.1.2.2 Examples of other African ports
        • 11.1.2.3 Examples of other major world ports
        • 11.1.2.4 Trade routes
          • Iron Ore
          • Coal
          • Grain
          • Oil
          • Containers
      • 11.1.3 International Time Zones & International Date Line
      • 11.1.4 Maritime-related Careers
        • 11.1.4.1 Sea-going Careers
    • 11.2 Shipping Operations
      • 11.2.1 Harbours as transport interface
      • 11.2.2 Ship operations
        • 11.2.2.1 Ship owning
        • 11.2.2.2 Ship management
        • 11.2.2.3 Ship broking
        • 11.2.2.4 Ship chartering
        • 11.2.2.5 Ship scrapping
        • 11.2.2.6 Shipbuilding
        • 11.2.2.7 Ship’s agency operations and procedures
        • 11.2.2.8 Bunkering
        • 11.2.2.9 Cargowork
        • 11.2.2.10 Stevedoring
        • 11.2.2.11 Ship repair and maintenance
        • 11.2.2.12 Ship chandling
        • 11.2.2.13 Salvage
      • 11.2.5 Voyage costs
    • 11.3 International Trade
      • 11.3.1 Principles governing trade and transport
      • 11.3.2 Major global areas of supply and demand
      • 11.3.3 Factors influencing trade fluctuations
      • 11.3.4 Procedures pertaining to shipping containers
      • 11.3.5 A Littoral State
    • 11.4 Maritime Environmental Challenges
      • 11.4.1 Environmental aspects which could affect maritime operations
      • 11.4.2 Influence of Weather Systems on shipping operations
      • 11.4.3 Fishing
      • 11.4.4 The Environmental Impact of the Extraction of Minerals, Oil, and Gas
      • 11.4.5 Alternative Energy Sources
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    About The Author

    From an early age, Brian Ingpen walked the wharves and jetties of Cape Town harbour, stimulating his fascination with ships and their cargoes. Time on tugs and aboard ships as a schoolboy made shipping a focus that naturally led him to the South African Navy for his national service [...] Read more

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