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Category Archives: Navigation



The sextant is an instrument used to measure angles. Its arc is one sixth of a circle. Hence it is called a sextant.In actual practice, the arc of the sextant is about 60°. Being an instrument of double reflection, it can measure angles up to

under keel clearance

Under Keel Clearance

A change in draught may arise during a voyage due to factors such as cargo and ballast changes as well as sea water density, and dynamic factors such as squat, pitch /roll etc. These factors should be considered in the appraisal and appropriate figures calculated

ecdis alarms


Below is the list of mandatory alarms / indication as per MSC Resolution 232(82). Alarm: An alarm or alarm system which announces by audible means, or audible and visual means, a condition requiring attention. Indicator: Visual indication giving information about the condition of a system

ENC chart correction


ENCs are updated by weekly ‘Notices to Mariners’ issued by Hydrographic Offices / Regional ENC co-ordination centers ( RENC) and corrections are received on the vessel either by email or data file (AVCS DVD). The actual updating is either applied to the ECDIS chart database

ECDIS detection area

ECDIS – Detection Area

A valuable function of ECDIS is to continuously display position fixes and at the same time, monitor a detection area ahead of the ship for hazards to navigation. This detection area may have a different name depending on the manufacturer, but common terms include‘safety frame’

tropical revolving storm

Storm Navigation

Finding the Quadrant – Northern Hemisphere Northern Hemisphere If the wind veers she is in the right hand semicircle (Dangerous Semicircle)If the wind backs she is in the left hand semicircle (Navigable semicircle) Navigable Semicircle Northern HemisphereProceed at maximum practical speed, alter courses as wind

Weather Routeing- Planning

Weather routeing is the procedure of ensuring that the ship makes an ocean passage in the least possible time conducive to the safety of the vessel. In order to do effective weather routeing the following steps must be considered⦁ Ships performance curves must be drawn⦁

ECDIS – Compilation Scale and Scale Minimum

During passage planning the 2nd officer plans a passage apparently clear of visible dangers to navigation. ( IGNORE SHALLOW CONTOUR SETTINGS ) Consequence : The deep draft aframax tanker drawing aft draft of 15.0 m goes aground in safer waters well clear of the visible

ECDIS – Contour Settings

Traditional method of passage planning on paper chart: Using a draft of 14 mtr and applying a 2 mtr safety margin, the second mate would mark off areas with depth 16 mtrs and less, on the navigational chart. These areas would then be highlighted, using

ECDIS (Safe or Risk to Navigation)

Numerous groundings and near misses have occurred on ECDIS equipped ships that could have been avoided but for failures in the setup and use of ECDIS. Like most of the world’s merchant fleet trading internationally, your ship(s) is most likely equipped with an Electronic Chart