Information available on Admiralty Routing Charts

Admiralty Routing charts are used in passage planning for ocean voyages, Routeing Charts include ocean routes and distances between major ports, ocean currents, ice limits, load lines and wind roses. They also contain expected meteorological and oceanographic conditions for each month of the year.

The data that is available on a Routing Chart are as follows :

Wind Rose on Routing Charts

Wind Rose is graphical depiction of wind data as regard to direction and force of wind likely to be encountered in an area, in a particular period of month.

With the help of the wind rose, it can be known at a glance the likelihood of encountering wind from a particular direction at a given force.

Wind Rose information on Routing Chart
Wind Rose information on Routing Chart

Wind roses are shown in red on routing charts, in the form a circle having arrows pointing radially towards center. The arrows fly with the wind, and this fact provides the direction. The length of the arrow indicates the percentage frequency of occurrence on the scale provided on the chart.

The thickness of the arrow indicates the wind force.

Ocean Currents - predominant direction and speed in knots

An Ocean current is the general movement of body of sea water on a permanent, semi-permanent or seasonal basis. Currents flow at all depths in the oceans, but usually the stronger currents occur in an upper layer.

The blue arrow show the predominant direction of sea surface currents during the period the Chart is prepared for. The Arrows show the constancy of the current. The average rate of the current is mention on the arrow on the chart in figures.

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Ocean currents on a Routing Chart
Ocean currents on a Routing Chart

The general surface current circulation of the world is shown on the World Climatic Charts in NP136 - Ocean Passages of the World and also described in Admiralty Sailing Directions.

Recommended Ocean Routes and distances

These recommended ocean routes marked on the Routing charts are between the Major Ports considering the statistics on weather, currents and climate.

Recommended shipping Routes and Distances
Recommended shipping Routes and Distances

Distances for the routes are between the indexed arrival and departure positions, to the nearest 10 miles for passages of more than 1000 miles and to the nearest 5 miles for distance less than 1000 miles. The arrival and departure positions are usually pilot grounds or anchorages, as mentioned in the Admiralty Sailing Directions.

Ice information - Maximum Ice Limits

Ice Limits is the climatological position of the extreme minimum or maximum of sea ice extent. Admiralty Routing Charts provides information regarding minimum limit of pack ice, average limit of pack ice, Maximum limit of pack ice and Mean maximum iceberg limit.

Ice limits markings on Routing Chart
Ice limits markings on Routing Chart

Mean Sea Temperatures / Dew point Temperature

Mean Sea and Dew point temperature are shown on a small Box on the Right side of the Routing chart. This is a pictorial representation using lines. Below image will help you understand.

Mean Sea Temperature and Dew point Temperature
Mean Sea Temperature and Dew point Temperature

Mean Air Temperature / Mean Air Pressure

Mean Air temperature is also represented on a small chart on Routing box on Right Side.

Mean Air Temperature and Mean Air pressure representation on Routing chart
Mean Air Temperature and Mean Air pressure representation on Routing chart

Load Line limits

Load Line limits are marked on Routing charts as per the Load line charts with respect to the Area covered in Routing Chart. Below is the pictorial representation

Lodline Limits representation
Lodline Limits representation

Percentage Frequency of Wind of Beaufort force of 7 and Higher / Storm Tracks

Percentage Freq. of winds of Beaufort scale 7 and Higher and TRS Storm Tracks
Percentage Freq. of winds of Beaufort scale 7 and Higher and TRS Storm Tracks

Low Visibility / FOG

Low Visibility mentioned on routing chart is the percentage frequency of visibility less than 5 miles  and fog mentioned as percentage frequency of visibility less than 0.6 miles approx.

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Low Visibility and Fog condition frequency mentioned in %
Low Visibility and Fog condition frequency mentioned in %

 

4 Replies to “Information available on Admiralty Routing Charts”

  1. How many charts are there.
    N&S Pacific
    N&S Atlantic
    Indian Ocean
    The Gulf of Mexico & Caribbean
    Malacca strait – Marshall Island
    Mediterranean & Black
    Total makes it 96.
    But on some site, I saw there are 144.
    Please confirm.

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