OVERVIEW OF NAVIGATION EQUIPMENTS USED IN SHIP

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A maritime vessel employs various types of electronic instruments for its navigation tasks. The primary functions of these instruments are to ascertain the position, speed, and direction of the vessel, calculate the time required to reach a destination, facilitate communication and signaling, prevent collisions and accidents, and manage distress situations effectively.

Herein lies an overview of essential navigation equipment that every Electro-Technical Officer (ETO) should be familiar with:

GYRO COMPASS

The Gyro Compass is a specialized device that utilizes a fast-spinning gyroscope powered electrically and operates using the fundamental principles of physics, including gravity and the Earth's rotation, to accurately determine true north.

MAGNETIC COMPASS

Operating based on the Earth’s natural magnetic fields, the magnetic compass allows the needle to respond effectively to these fields. As a result, the southern pole of the needle aligns with the Earth’s magnetic north pole, enabling navigators to ascertain their northern direction.

RADAR/ARPA

A marine radar combined with Automatic Radar Plotting Aid (ARPA) capability can monitor radar contacts and compute object trajectories, speeds, and closest points of approach (CPA), thus indicating potential collision risks with nearby vessels or land. Two radar bands used on vessels are:

• X-BAND: This band is often preferred for its compatibility with smaller antennas and superior target resolution at a frequency of 9GHz.
• S-BAND: Typically utilized in specialized scenarios where long-range bird detection or adverse weather penetration is necessary, operating at a frequency of 3GHz.

AUTO PILOT

The autopilot functions as a steering and heading control system utilizing a PID (Proportional Integral & Derivative) control mechanism. To operate, the vessel must be aligned to the desired heading, with a simple hold on the course followed by pressing the AUTO button. The autopilot will then memorize the course and make helm corrections to maintain it.

SPEED LOG

The speed log is crucial for measuring the ship's relative speed through water. Common types of speed logs on board include:

• DOPPLER LOG: Works on the principle of the Doppler Effect, transmitting ultrasonic waves in a bidirectional manner and calculating the Doppler shift for speed determination via SDME (Speed and Distance Measuring Equipment).
• ELECTRO-MAGNETIC LOG: Based on Faraday's Law of Electro-Magnetic Induction, this log measures induced electromotive force due to the relative motion of a conductor within a magnetic field.

ECHO SOUNDER

The Echo Sounder is an apparatus that incorporates a transducer fixed under the ship and a display unit showing the depth and seabed layout. Achieved through ultrasonic waves emitted and reflected off the seabed, it typically operates within the frequency range of 50KHz-200KHz.

AIS

The Automatic Identification System (AIS) was originally designed to support Vessel Traffic Services (VTS). It includes an AIS transponder, controller, and connection box, enabling communication of critical data such as the ship's name, type, position, and speed over ground to other AIS-equipped vessels.

DGPS

The Differential Global Positioning System (DGPS) enhances positional accuracy by utilizing beacon receivers that receive corrected data from a known GPS satellite transmitted by beacon stations.

NAVTEX

NAVTEX stands for Navigational Text Messages, providing short-range maritime safety information in coastal waters. Transmitted data includes navigational and meteorological warnings and other relevant information.

ANEMOMETER & ANEMOSCOPE

Anemometers gauge wind speed while anemoscopes indicate wind direction, collectively referred to as windicators. Types of anemometers include:

• FAN/VANE: Measures wind speed and direction using an AC generator and DC selsyn for the detection.
• CUP: Contains three wind cups spinning with wind pressure, and an encoder for determining wind direction.

ECDIS

The Electronic Chart Display and Information System (ECDIS) is an advanced navigation tool complying with International Maritime Organization (IMO) regulations, allowing for electronic charts that integrate data from multiple instruments like GPS, Gyro, RADAR, Echo Sounder, thus enhancing navigational reliability.

NAVIGATION LIGHTS

Navigation lights are crucial for indicating the ship's position and status during coastal navigation or in busy maritime areas to prevent accidents.

ALDIS

The ALDIS (All Day Light Signalling Lamp) is essential for Morse code signaling between vessels using halogen lamps.

VHF

Marine VHF radios facilitate two-way voice communication across ships and between ships and coastal stations using FM channels in the frequency range of 156 to 174 MHz.

BNWAS

The Bridge Navigational Watch Alarm System (BNWAS) monitors the vigilance of bridge officers, indicating a warning when no input is received within a set time, which then escalates to alarms requiring officer action to avoid potential accidents.

The aforementioned instruments serve specific navigation and communication purposes, while additional tools enhance maritime safety and security:

GMDSS

The Global Maritime Distress and Safety System (GMDSS) comprises various safety protocols and communication equipment designed to safeguard maritime operations and facilitate distressed vessel rescues.

EPIRB

The Emergency Position-Indicating Radio Beacon (EPIRB) allows for swift location in emergencies through distress signals. These battery-powered devices are designed to float and operate for at least 48 hours after activation, critical for maritime safety.

SART

A Search and Rescue Transponder (SART) activates autonomously upon detecting radar signals, significantly enhancing search efforts for distressed vessels.

VDR

The Voyage Data Recorder captures the navigational status for post-incident investigations and comes in two types: Fixed Protection Capsule and Float Free Capsule units.

LRIT

Vessels must report their positions to flag administrations multiple times daily, typically automated through existing satellite communication systems.

SSAS

The Ship Security Alert System (SSAS) improves vessel security by transmitting alerts to notify Rescue Coordination Centres upon triggering.

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