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Category Archives: Navigation

automatic identiciation system

Automatic Identification System

AIS is a system that transmits vessel position, course and speed via a VHF radio channel to all ships within range (typically up to 30 miles). It also receives similar information from other AIS equipped vessels within range. Automatic identification system (AIS) is fitted aboard

parallel indexing

Parallel Indexing

Parallel indexing is an effective way of monitoring a vessels progress along a preselected track using a radar. As a vessel moves on its chosen heading, fixed objects in its radar vicinity appear to be moving in a reciprocal direction to this motion. This technique

azimuth circle

Azimuth Mirror

A compass is equipment which is used to find direction while at sea. A compass tells the direction in which the ship is going or the direction of any other object. An azimuth mirror is used in conjunction with a compass. This device enables the

doppler log

Doppler Log

The speed log is a device used to measure the speed and also the number of nautical miles the vessel has travelled through the water in a given time. Type of speed measurements This is the speed of the vessel with respect to the solid

passage planning

Passage Planning For Pilotage Waters

90% of all the shipping casualties occur in coastal and port areas. The coastal passages leading to ports are generally the most dangerous portions of vessel voyages and vast majorities of marine casualties occur during this passage. It is therefore imperative that the bridge team

ecdis route check

ECDIS Route Check

The created route must be checked for potential dangers in case any have been overlooked during route creation. The system will conduct a check for charted dangers, unsafe depths and potential hazards only within the confines of the specified XTL. The check should consider all


Radar Best Practice -ARPA

When using the ARPA the following points to be considered: For collision avoidance purposes an ARPA should be sea stabilized with a log input delivering the vessel’s speed through the water. The resulting true vectors will provide a more accurate indication of the aspects of



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