CIS Colour Code
For several years, Ice Service Specialists have been applying a colour code to ice information charts for the
Canadian Coast Guard operations in the St. Lawrence River and the Gulf of St. Lawrence. The code has proven to
be quite beneficial to individuals making transportation decisions based on these charts. More recently, the
code has been modified and expanded to apply to all coastal waters of Canada, including the Arctic.
The Colour Code
The colour code is intended to assist navigation decisions in ice infested water. It is loosely based on the
concept of a traffic light, where green means proceed, yellow means caution and red signals danger. The
objective of the colour code application is to enable a person to quickly assess general ice conditions.
A ship sailing in a given area can easily assess the general ice conditions and, hence, qualify the difficulty
or ease to either navigate through easily, reduce speed or stop the ship.
However, this does not consider other variables (such as winds, currents or ship design) which are important
considerations in any ice navigation decision. The most detailed ice information continues to reside in the
ice egg codes.
How to Interpret the Code
The following information is intended to assist ship navigators with the interpretation of colour codes used
on ice charts.
Open or Bergy Water
Areas of open water or bergy water are coloured blue.
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Blue - open or bergy water |
Presence of Ice
For ice concentration of one tenth or greater, the ice type must be separated into two categories: less than 15 cm and greater than
15 cm thickness.
Ice Types Thicker than 15 Cm
The colour for a given ice area is determined by the total concentration of the ice types thicker than 15 cm.
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Green - from 1 to 3 tenths of ice thicker than 15 cm |
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Yellow - from 4 to 6 tenths of ice thicker than 15 cm |
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Orange - from 7 to 8 tenths of ice thicker than 15 cm |
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Red - from 9 to 10 tenths of ice thicker than 15 cm |
Presence of Old Ice
The presence of old ice (multi-year ice) is indicated by the colour purple.
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Purple Dash Lines - indicates the presence of 1 to 4 tenths of old ice |
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Purple Background - indicates the presence of 5 tenths or more of old ice |
Presence of Fast Ice
The presence of fast ice, regardless of the thickness is always black or grey.
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Black- fast ice regardless of thickness |
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Grey- fast ice regardless of thickness |
Ice Types Thinner than 15 Cm - No Colour Assigned in Background
Ice less than 15 centimetres in thickness is indicated by a star code. The colour of the stars is determined
by the amount of grey ice (10 to 15 cm) versus new ice (0 to 10 cm).
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Blue Stars - predominance of ice thinner than 10 cm |
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Red Stars - predominance of ice thickness between 10 and 15 cm |
Ice Types Thinner than 15 Cm - Colour Assigned in Background
Secondary ice types with less than 15 centimetres in thickness are indicated by a star code. The colour of
the stars is determined by the amount of secondary grey ice (10 to 15 cm) versus secondary new ice (0 to 10 cm).
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Blue Stars - predominance of secondary ice thinner than 10 cm |
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Red Stars - predominance of secondary ice thickness between 10 and 15 cm |
The star code is placed over top of the background colour. In the case of 9/10 to 10/10 of ice (red background)
and predominance of ice thickness between 10 and 15 cm (red stars), the stars and background blend together
and simply appear as a red background.
If further clarification is needed in interpreting the colour code, please contact the Canadian Ice Service
at 1-800-767-2885 (toll-free in Canada), by e-mail at cis-scg.client@ec.gc.ca, or by contacting
the nearest Canadian Coast Guard Ice Office.
