The sextant is a valuable instrument used to determine the angle between the horizon and a celestial body like the Sun, Moon or Star. It is used in celestial navigation to find out the latitude and longitude. 

Sextant derives its name from the Latin word’ sextus; or ‘one-sixth’, as the sextant’s arc spans  60° or one-sixth of a circle. Octans with 45° arcs were initially used to determine the latitude. However, Sextants were developed with wider arcs to calculate longitude from lunar observations. They replaced octants by the latter half of the 18th century.

It consists of an arc of a circle marked in degrees. It also has a movable radial arm pivoted at the circle’s centre. There is a telescope mounted to the framework, which is lined with the horizon.

A mirror is placed on the radial arm. It is moved or adjusted until the celestial body is reflected into a half-silvered mirror in line with the telescope and appears to coincide with the horizon through the telescope.

The angular distance of the celestial body or star above the horizon is read from the graduated arc of the sextant.

Mainly used at sea, the tool is so named because its arc is one-sixth of a circle – 60 degrees. It adheres to the principle of double reflection hence it can measure angles up to 120 degrees. Practically speaking, the arc of the sextant is a little over 60 degrees, and therefore the total angle measurable is about 130 degrees.

Sextant is an essential tool for celestial navigation and is also used by mariners to measure the angle between the horizon and a visible object (or two objects at sea).

Hold the sextant vertically and point it in the direction of the celestial body. See the horizon through an unsilvered part of the horizon mirror. Continue to move or adjust the index arm until the image of the star/sun, which has been reflected by the index mirror and then by the silvered portion of the horizon mirror, seems to rest on the horizon.

The altitude of the celestial body can be determined by reading from the scale on the arc of the sextant’s frame.

The sextant is used to measure the following:

1. Vertical Sextant Angle (VSA)
2. Horizontal Sextant Angle (HSA)
3. Altitudes

Brief History Of Sextant

A ship’s altitude above the horizon was related directly to the ship’s latitude. Mariners began to invent tools for measuring these factors to aid in navigation. One of the simplest was the kamal used by Arab navigators from the 6th century onwards. 

A 2-inch long rectangle board was used. A string with evenly spaced knots was attached to it. This arrangement was called a kamal. The navigator held the string using his teeth and moved this board farther from his body, aligning its bottom edge with the horizon and the top with the object, generally the Polaris or the north star.

The number of knots between the mouth and the board gave an idea of the relative height. Although kamal was quite useful, it was not precise enough and, by the 13th century, gave way to the astrolabe and the mariner’s Quadrant.

The Quadrant was popular with Portuguese explorers that travelled south along the African coast to search for a route to the Orient. 

When the seafarers reached close to the equator heading south, Polaris disappeared below the horizon. Hence, in the southern seas, mariners used another way to find their latitude. Per instructions from Prince Henry of Portugal, by 1480, Portuguese astronomers had found a way to determine the latitude using the position of the Sun when it moved north and south of the equator with changing seasons, what we now refer to as its declination.

To put it simply, the navigator could calculate the Altura or altitude and latitude by using his Quadrant to take the altitude of the Sun when it came to its highest altitude at local noon and then make a correction for the position of the sun north or south of the equator per the date. 

Columbus used it extensively on his voyages to the New World. He marked off the latitudes of places he visited, such as Lisbon, Serra Leoa, Cabo Verde and other places he might have landed. 

Also, it was common for navigators during those times to record the altitude of the Polaris in degrees at ports where they wished to return again. Hence, lists of alturas of many ports were published to guide the seafarers up and down the coasts of Africa and Europe.

Principle of the Sextant

1. When a ray of light is reflected by a plane mirror, the angle of the incident ray is equal to the angle of the reflected ray; when the incident ray, reflected ray and the normal lie on the same plane
2. When a ray of light suffers two successive reflections in the same plane by two plane mirrors, the angle between the incident ray and the reflected ray is twice the angle between the mirrors

Different Parts Of A Sextant

A sextant is shaped in the form of a sector (60 degrees or 1/6th of a circle). It is the reason the navigational instrument is called a Sextant (the Latin word for 1/6th is Sextans). The sector-shaped part is called the frame.

A horizontal mirror is attached to the frame, along with the index mirror, shade glasses (sunshades), telescope, graduated scale and a micrometre drum gauge.

How Does A Sextant Work And How To Use It?

Watch this video to understand how to use a sextant.

Navigation Sextant – Readings ON and OFF the arc

The normal graduations of the arc, to the left of zero, extending from 0 to 130 degrees, are referred to as ON the arc. To the right of 0 degrees, the graduations extend for a few degrees and are referred to as OFF the arc. When reading OFF the arc, graduations of the micrometer should be read in the reverse direction (59 as 1′, 55 as 1′ and so on).

Errors of the Sextant

The errors can be classified as

1. Adjustable Errors (adjustable onboard), and

2. Non-adjustable Errors (not adjustable onboard)

Adjustable Sextant Errors

• The Perpendicularity error : This is caused when the index glass is not perpendicular to the plane of the instrument. To check for this, clamp the index bar about the middle of the arc, and holding the sextant horizontally, with the arc away from you, look obliquely into the index mirror till the arc of the sextant and its reflection on the index mirror is simultaneous. If in alignment, the error does not exist. If not, turn the adjustment screw at the back of the index glass until they are aligned.

• Side Error: This is caused by the horizon glass not being perpendicular to the plane of the instrument. Clamp the index bar at 0 degrees 0.0′. Hold the sextant vertically and look at the heavenly body. Turn the micrometre one way and then the other while looking at the body. The reflected image of the body will move above and below the direct image and should pass exactly over it. If the reflected image passes to the left or right of the direct image, a side error exists. This error can be removed by turning the second adjustment screw (the top screw behind the horizon glass) until the true and reflected horizons appear in the same line.

• Index Error: This is caused if the index mirror and the horizon glass are not exactly parallel to each other when the index is set at 0 degrees 0.0′. Basically, this is the difference between the optical zero of the sextant and its graduated zero, termed OFF the arc if the optical zero lies to the right of the graduated zero and termed ON the arc if the optical zero lies to the left of the graduated zero. There are three methods of obtaining the index error of a sextant:
  
  A) By observing the horizon: Clamp the index at 0 deg 0.0′ and, holding the sextant vertical, look at the horizon. The reflected image and the direct image should appear in a perfect line. If not, turn the micrometer until they coincide exactly. The reading of the micrometre, ON or OFF the arc, gives the IE
  
  B) By observing the star or planet: Clamp the index at 0 deg 0.0′ and holding the sextant vertical, look at the star/planet. The reflected and direct image must coincide. If not, turn the micrometer till they do. The reading of the micrometre, ON or OFF the arc, gives the IE
  
  C) By observing the Sun: Set the index at about 32′ ON the arc. Hold the sextant vertically and look at the Sun, using shades. The reflected image of the Sun would appear below the direct image. Turn the micrometer until their closer limbs just touch. Note reading ON the arc.
  Set the index at about 32′ OFF the arc and look at the Sun. The reflected image of the Sun would appear above the direct image. Turn the micrometer until their closer limbs just touch. Note reading OFF the arc.
  The name of IE is the name of the reading having a higher numerical value.

• The error of Collimation: This is due to the axis of the telescope not being parallel to the plane of the instrument. The telescope is attached to the sextant in such a manner that it cannot tilt. These modern sextants are, therefore, not provided with any collimating screws

Non-Adjustable Errors Of Sextant

• Graduation Error: Due to the inaccurate graduation of the main scale on the arc or of the micrometre/vernier

• Centring Error: Caused if the pivot of the index bar is not situated at the geometric centre of the arc. This can be caused due to a manufacturing defect or due to careless handling.

• Shade Error: The shades should be so mounted that their glass surfaces are normal to the rays of light passing through them. If not, the distortion would result. The greater number of shades used, the greater the chances of distortion.  

• Optical Errors: Caused by prismatic errors of the mirrors or aberrations in the telescope lens

• Wear on the rack and worm: This causes a backlash, leading to inconsistent errors. Wearing down of the worm can be due to lack of lubrication, the presence of dust particles, careless handling.

Dip

This is the angle at the observer between the plane of the observer’s sensible horizon and the direction of his visible horizon. A dip occurs because the observer is not at sea level. The value of the dip increases as the height of the eye of the observer increases. The values of dip are given on the cover page of the nautical almanac and in nautical tables (Nories) as a function of the height of the eye.

Pointers on the use of a sextant

1. Always check the errors before use
2. Focus the telescope while looking at the horizon and make a mark on the circumference of the stem
3. During use, hold the sextant steady. For this, stand with feet slightly apart for balance with hands holding the sextant steady
4. While observing the altitude of a celestial body, remember to swing the sextant to the other side; the body will appear to move along the arc. Measure the altitude at the lowest point on this arc
5. Stand as close as practicable to the centerline of the ship
6. Use appropriate dark shades while observing the Sun
7. If a backlash error exists, remember to rotate the micrometer in one direction only
8. Altitudes of stars and planets should be taken during twilight
9. Nighttime sextant observations should be avoided as far as practicable. The strong moonlight gives the illusion of a good horizon which is most probably false
10. While observing the HSA, set the index at zero, look at the object on the right through the telescope, gradually swing the index around and finish while facing the object on the left
11. When measuring VSA, look at the top of the object, set the index at zero and look at the top of the object. VSA = height of the object in meters
    1852 X Tan VSA

Care and maintenance of a sextant

1. Do not put too much stress on the index bar when grasping a sextant
2. Never touch the arc. It will smear it. These aren’t oleophobic per se
3. Ensure that the worm and rack are clean
4. Coat worm and rack with Vaseline when not using it for too long
5. Mirrors, lenses and shades should be wiped clean with a soft cloth
6. After each use, gently wipe the index mirror, horizon glass
7. Put it in the box when not using it
8. Do not bump the sextant anywhere
9. Avoid exposure to sunlight
10. Keep sextant stowed away from direct sunlight, dampness, heaters or blowers

The sextant is an expensive, precision instrument which should be handled with utmost care.

Reference: Principles of Navigation by Capt. Joseph & Capt. Rewari, The Marine Sextant by Capt. H. Subramaniam

You may also like to read – An Introduction to Fluxgate Compass 

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

A Comprehensive Guide to Marine Sextant – Principles, Usage, and Maintenance appeared first on Marine Insight - The Maritime Industry Guide

The world of AIS (or Automatic Identification System) can often be a confusing one to delve into, with many questions arising, such as “what is AIS?” “why do I need it?” and “what type of AIS does my ship need or have?”

An automatic Identification System (AIS) is an automated tracking system that displays other vessels in the vicinity. The broadcast transponder system operates in the VHF mobile maritime band.

Your ship also shows on the screens of other vessels in the vicinity, provided your vessel is fitted with AIS. If AIS is not fitted or not switched on, there is no exchange of information on ships via AIS.

The AIS onboard must be switched on at all times unless the Master deems that it must be turned off for security reasons or anything else. The working mode of AIS is continuous and autonomous.

Why is AIS provided?

It is fitted on ships for the identification of ships and navigational marks. However, it is only an aid to navigation and should not be used for collision avoidance. Vessel Traffic Services (VTS) ashore use AIS to identify, locate and monitor vessels. The Panama Canal uses the AIS to provide information about rain along the canal and wind in the locks.

SOLAS Requirements

The IMO Convention for the Safety Of Life At Sea (SOLAS) Regulation V/19.2.4 requires all vessels of 300 GT and above engaged on international voyages and all passenger ships, irrespective of size, to carry AIS onboard.

AIS Types

1. Class A: Mandated for all vessels 300 GT and above engaged on international voyages as well as all passenger ships
2. Class B: Provides limited functionality and is intended for non-SOLAS vessels. Primarily used for vessels such as pleasure crafts

AIS operates principally on two dedicated frequencies or VHF channels:

• AIS 1: Works on 161.975 MHz- Channel 87B (Simplex, for the ship to ship)
• AIS 2: 162.025 MHz- Channel 88B (Duplex for the ship to shore)

It uses Self Organizing Time Division Multiple Access (STDMA) technology to meet the high broadcast rate. This frequency limits the line of sight, which is about 40 miles.

Working Of AIS

How does AIS work exactly? How do we obtain all this data?

Originally, AIS was used terrestrially, meaning the signal was sent from the boat to land and had a range of roughly 20 miles (also considering the earth’s curvature). As ships began sailing further away from land, they started sending the signal to low orbit satellites, relaying information back to land. This meant ships could sail as far as they liked, and we’d always have peace of mind knowing exactly where they were and how they were doing.

The AIS system consists of one VHF transmitter, two VHF TDMA receivers, one VHF DSC receiver, and a standard marine electronic communications link to shipboard display and sensor systems. Position and timing information is normally derived from an integral or external GPS receiver. Other information broadcast by the AIS is electronically obtained from shipboard equipment through standard marine data connections.

Although only one channel is necessary, each station transmits and receives over two radio channels to avoid interference and communication loss from ships. A position report from one AIS station fits into one of 2250 time slots established every 60 seconds. AIS stations continuously synchronize themselves to avoid overlap of slot transmissions.

It’s pretty easy to install as well, as AIS is generally integrated with ship bridge systems or multifunctional displays, but installing a standalone system is as straightforward as plugging in a couple of cables and switching on the plug.

Data Transmitted

1. Static Information (Every 6 minutes and on request):

• MMSI number
• IMO number
• Name and Call Sign
• Length and Beam
• Type of ship
• Location of position fixing antenna

2. Dynamic Information (Depends on speed and course alteration)

• Ship’s position with accuracy indication
• Position timestamp (in UTC)
• Course Over Ground (COG)

3. Voyage Related Information (Every 6 minutes, when data is amended or on request)

• Ship’s draught
• Type of cargo
• Destination and ETA
• Route plan (Waypoints)

4. Short safety-related messages

• A free-format text message addressed to one or many destinations or all stations in the area. This content could be such as buoy missing, iceberg sighting etc

AIS as a surveillance tool

In coastal waters, shoreside authorities may establish automated AIS stations to monitor the movement of vessels through the area.

Coast stations can also use the AIS channels for shore to ship transmissions and to send information on tides, NTMs and located weather conditions.

Coastal stations may use the AIS to monitor the movement of hazardous cargoes and control commercial fishing operations in their waters. AIS may also be used for SAR operations enabling SAR authorities to use AIS information to assess the availability of other vessels in the vicinity of the incident.

AIS as an aid to collision avoidance

AIS contributes significantly to the safety of navigation. All the information transmitted and received enhances the effectiveness of navigation and can greatly improve situational awareness and the decision-making process.

As an assistant to the OOW, the tracking and monitoring targets by the AIS and determining information on the CPA and TCPA add great value to the safety of navigation overall.

However, the user should not rely solely on the AIS information for collision avoidance. AIS is only an additional source of information for the OOW and only supports the process of navigating the vessel. AIS can never replace human expertise on bridges!

Limitations of AIS

As with all navigational and/or electronic equipment, the AIS has limitations:

1. The accuracy of AIS information received is only as good as the accuracy of the AIS information transmitted
2. The position received on the AIS display might not be referenced to the WGS 84 datum
3. Over-reliance on the AIS can cause complacency on the part of the OOW
4. Users must be aware that the AIS might transmit erroneous information from another ship
5. Not all ships are fitted with AIS
6. The OOW must be aware that AIS, if fitted, might be switched off by a certain vessel, thereby negating any information that might have been received from such a ship.
7. It would not be prudent for the OOW to assume that the information received from other ships might not be fully accurate and of precision that might be available on its vessel.

To sum it up, the AIS only improves the safety of navigation by assisting the OOW/VTS or whatever entity. It’s pretty easy to install as well, as AIS is generally integrated with ship bridge systems or multifunctional displays, but installing a standalone system is as straightforward as plugging in a couple of cables and switching on the plug.

There’s a lot more to AIS than meets the eye, we delve more into depth with the accompanying handbook both for beginners and those more well-versed in the world of AIS.

Download the Definitive Handbook on AIS by Big Ocean Data below for information:

Download the Guide to AIS here

Frequently Asked Questions (FAQs)

1. How does the AIS system work?

AIS works by taking the vessel’s location and movements through its GPS or the internal sensors built into the AIS unit. It is fitted on ships for the identification of ships and navigational marks. However, it is only an aid to navigation and should not be used for collision avoidance.

2. What are the types of AIS?

There are two classes of AIS, A and B. The former is Mandatory for all vessels 300 GT and above engaged on international voyages and all passenger ships. The latter provides limited functionality and is intended for non-SOLAS vessels. It is mainly used for pleasure crafts.

3. What is an AIS?

In simple words, an automatic identification system transmits a vessel’s position so that the other ones in the vicinity are aware of its position. International Organizations like IMO mandate that big commercial ships use an AIS for security reasons and to avoid collisions with other ships.

4. What are the data categories of an AIS?

AIS Data is divided into three categories: static data, which consists of information about the ship’s characteristics. The second is dynamic data which is ever-changing due to the constant movement of ships, and the last is the current voyage-related data.

5. How to use an AIS onboard a vessel?

The AIS must be switched on at all times unless the Master decides that it should be turned off for security purposes. The AIS constantly interprets and updates data, making it an essential tool on a ship.

You may also like to read. 

• What is IMO’s Global Integrated Shipping Information System (GISIS)?
• Watch: How Automatic Identification System (AIS) Helps Ships At Sea?
• What is Electronic Chart Display and Information System (ECDIS)?
• 8 Maritime Systems That Ensures Ship Safety And Security
• The Importance of Vessel Tracking System
• Watch: MOL To Install Voyage Information Display System Using AR Technology

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

What is Automatic Identification System (AIS)- Types And Working (FAQs) appeared first on Marine Insight - The Maritime Industry Guide

Looking for a handheld marine GPS device for your next expedition? You have come to the right place.

The advent of technology has resulted in a vast improvement in navigation tools used at the sea. In the marine industry, one technological development that has pioneered navigation is the Global Positioning System (GPS). Although conventional GPS systems are connected to computers, furtherance in the technology has led to the innovation of handheld marine GPS.

There are many GPS manufacturing companies that create and market such as portable marine GPS. But then there are those few elite ones that not only market a portable GPS navigator but ensure that these navigators are the best amongst their technological peers.

What are handheld marine GPS and its uses?

A GPS handheld device is very important at sea in order to locate your exact place and also in events of some crisis.

A marine GPS handheld device can help seafarers guide their boats in coastal areas as well as deep seas. It also enables both commercial and recreational fishermen to locate fishes as many GPS devices some with fish finder feature.

So what are the best GPS handheld devices in the market? You would see that Garmin devices dominate the list, but that is also because they are the best in the field and make reliable devices you can rely on.

Pros and cons of marine handheld GPS 

Pros –

• You can carry maps in a handheld device
• You can even know your altitude
• Handheld GPS is easy to use. You don’t need to be tech-savvy.
• Help you enhance your navigation skills
• Helps prevent dangers and in time of emergencies.

Cons –

• These are sometimes not rugged and can get damaged easily when dropped
• Some require maintenance
• Battery life can sometimes be an issue
• Expensive devices

Main Features of a GPS device

• Realtime tracking
• Trip history
• Alerts
• Anytime anywhere, access
• Geo-fencing
• Reports of historical events
• User-friendly interface

Mentioned in here are five best portable handheld marine GPS in the market today:

1. Garmin eTrex 20x

Garmin eTrex 20 x 65k has 240×320 pixels with a striking display that guarantees sharp pictures in direct daylight and stormy climate conditions.

The preloaded base guide is an additional feature that is highly useful.

It comes with a 3.7 GB of capacity to store your extra maps and sort out the maps any way you need. It is easy to locate and the GLONASS backing empowers high-accuracy and quick find in any event of an emergency

Pros:

• Sunlight readable 240×320 pixels display
• A decent size (up to 3.7 GBs of inward memory + microSD opening)
• Preloaded overall maps
• HotFix Satellite expectation and GLONASS support

Cons:

• Not all subtleties of maps are accessible
• Lack of manuals
• Does not accompany an extra SD card

Garmin eTrex 20x, Handheld GPS Navigator, Enhanced Memory and Resolution, 2.2-inch Color Display, Water Resistant

• UPGRADED DISPLAY - Features a 2.2” 65K color sunglight readable display offering increased resolution (240 x 320 pixels)
• LOAD MORE MAPS - Large 3.7 GB of internal memory and microSD card slot lets you load a variety of maps, including TOPO 24K, HuntView, BlueChart g2, City Navigator NT and BirdsEye Satellite Imagery (subscription required)
• PRELOADED BASEMAP - Includes a worldwide basemap with shaded relief. Display size:1.4 x 1.7 inches
• KEEP YOUR FIX - With its high-sensitivity, WAAS-enabled GPS receiver, HotFix satellite prediction and GLONASS support, eTrex locates your position quickly and precisely and maintains its location even in heavy cover and deep canyons
• Included Components: Documentation

Check Price on Amazon

2. The Garmin Inreach Explorer+

These handheld GPS units are fundamental to adventures such as boaters, mountain dweller etc. The information from this powerful device enables clients to decide their area, altitude, and other significant data that are valuable in wayfinding. The Garmin Inreach Explorer+ has worldwide Iridium satellite inclusion, which permits 2-way informing utilizing content from virtually anyplace on the planet.

The device is furnished with an original SOS work, which can be activated to send message to 24/7 search and rescue monitoring centre. The unit enables your loved ones to keep a track of you. The device can be combined with cell phones, for example, mobile phones and PCs, utilizing the Earthmate application, which comes free with the device. This enables you to download maps, outlines, and aerial pictures.

Pros –

• The overall inclusion gave by the device’s Iridium satellite system association offers clients a chance to keep in contact with loved ones from anyplace.
• A barometric altimeter decides altitude just as scope and longitude.

Cons –

• The vast majority of this current device’s preloaded maps are US-based so that it won’t be as helpful outside of the nation.

Sale

Garmin 010-01735-10 inReach Explorer+, Handheld Satellite Communicator with Topo Maps and GPS Navigation

• 100 percent global Iridium satellite coverage enables two way text messaging from anywhere (satellite subscription required)
• Trigger an interactive SOS to the 24/7 search and rescue monitoring center
• Track and share your location with family and friends. Water rating : IPX7. Battery : Rechargeable internal lithium ion
• Pair with mobile devices using the free earthmate app for access to downloadable maps, U.S. NOAA charts, color aerial imagery and more
• In reach explorerplus device adds preloaded Delorme topo maps with onscreen GPS routing plus built in digital compass, barometric altimeter and accelerometer

Check Price on Amazon

3. Garmin GPSMAP 64st

The daylight Readable 2.6 display helps with reading clear information, paying little respect to the hour of the day, sunlight, and climate conditions. It also comes with internal memory to store numerous maps in the inward memory of the device, without requiring a microSD card. The dual battery framework guarantees longer working hours, utilizing two batteries where you can transform one while the device is working and smart notifications – contains a temperature sensor, an altitude sensor, and accelerometer.

Pros –

• 16h of battery life
• Ability to charge the device while it is working.
• TOPO U.S. 100K + BirdsEye Satellite Imagery membership for nothing
• Wireless and Bluetooth support
• 3-pivot compass with barometric altimeter

Cons:

• Pricy
• A remote association requires a solid cell phone GSM signal
• Lack of complete manual
• Occasional GPS signal interruption

Garmin GPSMAP 64st Worldwide Handheld GPS with1 Yr. Birdseye Subscription and Preloaded TOPO U.S. 100K Maps + 32GB MicroSD Memory Card Bundle

Check Price on Amazon

4. Garmin GPSMAP 78sc

This marine handheld unit is an absolute necessity have device for any individual who needs to monitor courses while surfing water. The unit incorporates a splendid 2.6-inch display with high affectability GPS recipient and implicit base guide. Other significant highlights are 1.7 GB inward memory, information stockpiling, and microSD card space.

A decent quality marine GPS tracker, GPSMAP 78sc is incredibly convenient when at sea. High quality and sturdiness are excellent advantages provided by this GPS tracker.

Pros:

• GPSMAP 78sc, is intended to last more. Made out of reliable and robust materials
• Value for money
• A large portion of the marine GPS trackers out there comes at a substantial cost. But the GPSMAP 78sc is valued in the unobtrusive range to suit the spending limit of all classes of purchasers
• A robust 1-year guarantee upholds the GPSMAP 78sc. If something turns out badly with the device, you can call the seller and have the issues fixed without paying anything extra.

Cons:

• A few people confronted issues with the utilization of the device. In any case, that is not an issue. A little consideration on your end can resolve this minor issue.

Sale

Garmin GPSMAP 78sc Waterproof Marine GPS and Chartplotter

• Marine-friendly handheld with high-sensitivity GPS receiver and 2.6-inch color TFT display
• Perfect for boating/watersports--waterproof to IPX7 standards; floats in water
• Built-in BlueChart g2 U.S./Bahamas coastal charts with shorelines, depth contours, navaids, harbors, marinas, and more
• Built-in 3-axis tilt-compensated electronic compass and barometric altimeter for heading/altitude/weather
• Share your waypoints, tracks, routes and geocaches wirelessly with other compatible device user

Check Price on Amazon

5. Garmin GPSMAP 78S

The Garmin GPSMAP 78S comes with a high sensitivity GPS receiver with 2.6 inch color display. This device floats in water if gone overboard and thus is perfect of sailors.

With built-in BlueChart g2 U.S./Bahamas coastal charts with shorelines, depth contours, navaids, harbors, marinas, and more, it is perfect of smooth navigation.

Pros:

• Floats in water
• Adding maps to microSD card is easy
• Can share your waypoints, tracks, routes and geocaches wirelessly with other compatible device users

Cons:

• Vision can sometimes get blurry
• Smaller screen size
• Only US Maps

Sale

Garmin GPSMAP 78S Marine GPS Navigator and World Wide Chartplotter (010-00864-01)

• 2.6-inch TFT LCD display. Display size-1.43 x 2.15 inches. 2.6 inch diagonal
• Worldwide shaded relief basemap; microSD card slot for optional mapping
• 3-Axis compass & barometric altimeter
• Floats, buoyant
• Built-in 3-axis electronic compass; Barometric altimeter

Check Price on Amazon

6. Garmin GPSMAP 86Sci

The Garmin GPS 86Sci though a bit pricey is one of the finest marine handheld devices in the market. It is a water-resistant and floating device, with a sunlight-readable 3-inch display.

Enabled with satellite communication, it comes with two-way text messaging via the 100% Global Iridium satellite network.

It also comes with a 24×7 SOS service.

Pros:

• Brilliant menu arrangement; quick access to highlights
• Splendid screen
• Preloaded charts
• Wireless connectivity

Cons:

• Doesn’t work with standard mounts

Sale

Garmin GPSMAP 86Sci, Floating Handheld GPS with Button Operation, Preloaded BlueChart G3 Coastal Charts And Inreach Satellite Communication capabilities, Stream Boat Data From Compatible Chartplotters

• Water-resistant, floating design, sunlight-visible 3” display and button operation provide ease of use on the water
• Stream boat data from compatible chartplotters and instruments to consolidate your marine system information
• Preloaded bluechart G3 coastal charts include the best of Garmin and Navionics data
• Stay in touch with in reach satellite communication and two-way text messaging via the 100% Global Iridium satellite network (satellite subscription required)
• Functions as a remote control for convenient operation of your Garmin autopilot and Fusion Marine products; to activate, download free apps from our Connect IQ store

Check Price on Amazon

7. Garmin GPSMAP 86i

This premium marine handheld GPS device comes with 3″ sunlight-readable display along with amazing battery backup. It is a water-resistant and floating device with two-way text messaging via the 100% Global Iridium satellite network.

With worked in inReach satellite innovation and extra assistance options¹, GPSMAP 86i encourages you to keep in contact with your loved ones universally.

Pros:

• Water-safe,  floating design
• Keep in contact with two-way content informing using the 100% worldwide Iridium® satellite system (satellite membership required)

Cons:

• Pricey

Sale

Garmin GPSMAP 86i, Floating Handheld GPS with Button Operation, Inreach Satellite Communication capabilities, Stream Boat Data From Compatible Chartplotters

• Water-resistant, floating design, sunlight-visible 3” display and button operation provide ease of use on the water
• Stream boat data from compatible chartplotters and instruments to consolidate your marine system information
• Stay in touch from anywhere with in reach satellite communication and two-way text messaging via the 100% Global Iridium satellite network
• Functions as a remote control for convenient operation of your Garmin autopilot and Fusion Marine products; to activate, download free apps from our Connect IQ store
• Supports optional bluechart G3 charts

Check Price on Amazon

Each of these best portable marine handheld GPS systems provides the ultimate user satisfaction and features for a safe voyage, unlike any other portable marine GPS.

You may also like to read – An Introduction to Fluxgate Compass 

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

7 Best Handheld Marine GPS in 2024 appeared first on Marine Insight - The Maritime Industry Guide

Consumers’ Marine products involve using various essential and relevant equipment in marine travel, without which marine adventuring and travel can become risky. Consumers Marine, as the name suggests, caters to the consumers of marine travelling, offering them the necessary support system and technological back-up required to maintain their intended route and position in the water.

And the equipment offered to Consumers Marine is vast in terms of variety, so potential clients and users might get to choose their marine equipment from a more extensive collection than a smaller one. Of all the types of equipment involved, the three main ones that form the core of Consumers Marine are the Marine VHF Radios, Marine GPS Systems and the Marine Autopilots.

All the three above-mentioned Consumers Marine equipment are essential and relevant in their way and, in contemporary times, have gone a long way in easing the complexity of travelling through waters.

Marine VHF Radios

VHF means very high frequency and is an important component of marine mobile radio service which is used for sending a distress message by seamen. Marine VHF Radios are two-way communicators that transfer and receive messages to and from the responding station. It has a VHF antenna which transmits high-frequency waves, measured in MHz. VHF radio can range up to 30 nautical miles if the antenna is high enough.

However, the most critical function of a Marine VHF Radio is that it is beneficial when sending distress signals across the channels to coast guards and other ships and boats in the periphery. Also, specific Marine VHF Radios can be used to make calls through a marine operator for a certain sum making it double up as a telephonic communicator.

Another vital aspect of Marine VHF Radios comes in two main categories: portable and non-portable. Some also have an inbuilt GPS receiver and an AIS receiver too. A handheld VHF radio has waterproof coverings and is battery-operated to facilitate power transmission. So even if they fall into the water, they can float and still function.

The fixed or the non-portable VHF marine Radios cover a lot of aerial ground. Their power transmission and energy source are enormous compared to their portable counterparts and are far more feasible regarding their operational facilities.

Fixed radios also offer the Digital Selective Calling or dsc feature, which sends your location to the nearest coast guard with the push of one button. However, for this function, the radio should have its internal GPS receiver or be connected to another GPS on a boat, like a chart plotter.

To take maximum advantage of dsc radio, one should have a maritime mobile service identity or mmsi number, which can help you to connect with other vessels in the vicinity.

All boaters and sailors are required to have a VHF Radio on board their vessel, per United States Coast Guard. Most radios offer full international coverage with three maps of the USA, Canada and international waters.

How to use a VHF Radio

Always perform a radio check to ensure that it is working correctly. However, channel 16 should not be used for this. The radio should be turned to a one-watt power setting, and the microphone should be keyed. Call ‘radio check thrice along with the vessel name and the location. Then you can wait for the reply.

You can use a calling channel depending on the nature of the distress and the kind of assistance needed. A ship wanting to call a boater can do so on channel 9, and anybody, including boaters, can call a commercial vessel or shore via channel 16. This regulation prevents congestion on channel 16, the distress, safety and calling frequency. Also, boaters must maintain a watch on either channel 9 or 16 when the radio is on and not communicate with any station.

When using a VHF Radio during an emergency, tune it to channel 16 and full power. If your life is in danger, you can make a distress call by saying “Mayday Mayday Mayday,” the name of the vessel and call sign. After the coast guard responds, reply with the position of the vessel, ideally with your latitude and longitude from the GPS. A rescue boat can find you easily if the distress call offers complete information.

If you are not in a life-threatening situation but a bad position, say “pan-pan.” You can also give additional information such as vessel movement, speed, destination and number of people requiring medical attention and tow, the colour hull, cabin etc. Repeat in intervals if you do not receive an answer from the other side.

According to the Telecommunications Act of 1996, recreational boaters can use a VHF radio, an EPIRB and marine radar without an FCC ship station license.

Marine GPS Systems

Marine GPS Systems have become an essential apparatus for marine travel. Just like their counterparts fixed in cars, Marine GPS Systems help ships and boats stay on course, especially in areas where marine life forms thrive.

Importance of Marine GPS Systems

Everyone should have a GPS onboard, even when sailing on a small boat near the coast. Conditions at sea are everchanging, and mechanical failure or bad weather is possible. Also, modern GPS is not very expensive.

Most people might ask, why buy a GPS when you have one on your cellphone? However, mobile phones have many drawbacks. They are not fixed on your vessel. They might break or get damaged by strong waves, they are not waterproof, and their batteries die fast. Hence, GPS is essential life-saving equipment when you are at sea. Even non-professionals, recreational boaters and fishers should have a GPS with them.

Miscellaneous uses of GPS

Apart from showing your real-time location, GPS has other uses too.

For boaters, it can be used for setting up anchor alarms. You can make a geofence around your boat while it’s anchored, and if it gets loose and breaks the geofence, the alarm is triggered. Hence, it can function as a security system and even if you are away from it, if someone tries to steal it, you get a text message on your phone.

If it is connected to other electronic devices, it can offer other functions too. For instance, it can allow the autopilot to steer the course and provide additional data on the digital charts. It can give the VHF radio the position data of your vessel.

Also, Marine GPS Systems enable shipmen to pinpoint the location of other ships to avoid any collision in the waters and thus cause damage to people and cargo aboard the vessel. It is important to note that Marine GPS Systems come with protective waterproofing, have buttons and dials that can be operated even through gloves and offer easy usability to all marine travellers.

The accuracy of GPS depends on many factors, including atmospheric conditions, receiver quality etc. Once operational, a GPS continuously updates your location while offering speed and directional information. It also enables sailors and boaters to permanently save locations, commonly known as waypoints, to mark a fishing hotspot, a reef, etc. One can also make a waypoint route to reach points A to Z.

While earlier GPS showed position in terms of latitude and longitude, their modern counterparts show the location as a digital chart, much like you see your location on a street map on your mobile phone.

Such GPS, also called chartplotters, have comprehensive and detailed maps with great accuracy.

Marine Autopilots

Marine Autopilots form the third and final support system of Consumers Marine. In the old days, a ship had to be physically manoeuvred by the captain, leaving no scope for the captain to mingle with the rest of the ship’s crew. In contemporary times, however, the emergence of Marine Autopilots has solved the problem of physically manoeuvring the ship or the boat, thus allowing the captain far more flexibility in his operations.

Marine Autopilots are available in a wide array of forms. They can be classified from complex models to simple ones, thus offering support not only to experienced seafarers but also to newer and fresher ones. Marine Autopilots also rely on Marine GPS Systems, thus making these two types of equipment dependent on each other to a larger extent.

The recent expectations of Consumers Marine reflect the development and evolution that has taken place in marine travelling. As times have changed, the demand for products and equipment by Consumers Marine has also changed. In today’s times, equipment like Marine VHF Radios, Marine GPS Systems and Marine Autopilots has become the core necessity of any marine travelling because without them, one can get lost in the huge maze of water surrounding the earth – both as well as symbolic.

Frequently Asked Questions

1. What is the range of a VHF marine radio?

It is used for contacting rescue services, docks, harbours, marinas, nearby vessels etc. It operates in a high-frequency range between 156 and 162.025 MHz, with a connecting range of 25 to 30 miles.

2. Which VHF channel should you avoid using as a working channel?

You should avoid channel 16 as it is the most crucial channel, used as national distress, safety and calling frequency.

3. What is the importance of GPS in the maritime industry?

The Global Positioning System has changed how the world operates, especially marine search and rescue, which has become relatively easier and quicker. GPS offers the fastest and the most accurate way for mariners to navigate and measure speed and location.

4. Can you use a GPS with a transducer?

Yes, you can still use the GPS. However, the transducer/sonar or the depth finder will not function. Hence, one must have a transducer since it performs a vital function.

5. Do all sailboats have marine autopilots?

New sailboats usually have pre-installed autopilot; however, you can get one installed on older boats. Different autopilot systems are used for other boats. It is helpful on long sailing trips and saves lots of energy.

You might also like to read

• 30 Types of Navigation Equipment and Resources Used Onboard Modern Ships
• What are SSB Radios? 

• New eBook Launched – A Complete Guide to Travel Safety for Seafarers (With FREE Checklists)

• 12 Things a Smart Mariner Would Do Before Joining a Ship

• Marine Teaching Profession – Getting A Much-Needed Face-Lift

Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

References: Vhfradios, Gpstrackingdevices, Yatchingmagazine

What Are Marine VHF Radios, Marine GPS and Marine Autopilots? appeared first on Marine Insight - The Maritime Industry Guide

Handling a ship in currents, wind and tide is always a tricky affair. All these three factors can laterally shift the vessel from its course. A ship’s pilot has to keep an eye to these effects and constantly take remedial measures for safe navigation of the ship.

Berthing in heavy wind and tide situations is generally assisted by tags – be it a towing tug or a checking tug or a tug that imparts athwartship force to counter lateral drift. These are additional to the already existing ship’s engines, rudder and thrusters (if installed).

Now at any given time, the berthing speed is always on the lower side. It is best to keep it less than two knots under most circumstances. Bow or stern thrusters, which impart lateral or athwartship forces, are effective only when the speed is on the lower side. They dampen the impact of the vessel when it falls on the pier or berth.

When the bow is falling heavily on the jetty, the bow thruster is run to port or starboard, as the case may be so that the fall is restricted and lines are passed safely with the heaving lines, jolly boat or motor boat from the bow.

When a ship is taken astern, which a ship’s pilot normally does when he approaches the jetty, the ship’s stern goes either to port or to starboard. Consequently the bow goes in the reverse direction i.e. starboard or port. This effect is called canting.

For a vessel with a right handed propeller, i.e. for a propeller that rotates clockwise while the vessel goes ahead, the stern cants (swings) to port and the bow to the starboard. The reverse happens for a left handed propeller. At this stage the bow thruster comes to play. The bow in the first case is given to port so that its swing to starboard is restricted while in the second case it is given starboard.

One might ask why the bow and the stern swings while the ship comes astern? This is because of the transverse thrust and screw race effects which will be dealt with in another chapter.

Now bow thrusters are driven by motors. The power of the bow thruster generally depends upon the power of the motor. An 800 to 1000 HP Bow Thruster (BT) is effective enough to be fitted into a vessel having a LOA of 150-160 m and beam of 22-25 m with a GRT of about 10000-12000. It can counter easily offshore winds of 3-4 Beaufort (11 knots) while berthing.

In areas of higher wind speed and ships having higher LOA and GRT, a more powerful bow thruster (BT) is required.

Bow thrusters (BT) are generally installed to replace the use of tugs, which are hired by the vessels coming to port. It reduces the operating cost of the vessel. But in some ports, hiring a tug is mandatory. In that case, the BTs work as additional help to the ship’s pilots.

While anchoring, the BTs also play an important role, so as while turning. While anchoring, the bow is kept at a distance from the anchor chain using BT.

While turning a vessel, BT plays an important part. In restricted space like in a congested dock, the vessel has to literally spin on its axis. In such case the vessel is stopped and with the help of bow thruster the bow is swung to port or starboard, pivoting the stern.

Sometimes, the stern is also rotated with the rudder and engines. But what is generally considered in this case is the vessel’s natural tendency to cant while coming astern. If the vessel has a right handed propeller, the vessel’s bow will swing to starboard, while the engine is run astern. So it is always advisable to turn on the starboard wheel as while coming astern also, the vessel will keep turning in the desired direction.

While backing down, it is however advisable to take a towing tug at the stern and use the bow-thruster as and when needed. The tug straightens the stern as it pulls and any effects of transverse thrust are thus neutralized.

Bow thruster thus plays an important role in manoeuvring of ships. But how and when it should be used depends on the experience which has to be acquired on the field.

How Bow Thruster is Used for Maneuvering a Ship? appeared first on Marine Insight - The Maritime Industry Guide

One of the primary factors -external to the ship’s mechanical or electrical systems – that come in to effect while berthing a vessel is the marine fender system. An efficient fender system saves the ship from external damages that would have otherwise occurred to the hull plates or to the berth or jetty, which comes in contact with the steel plates of the ship.

How Ship Berthing is done Using Marine Fenders?

Theoretically speaking, a ship is to be brought at a negligible speed to the berth. A small increase in speed will give rise to an exponential jump in the momentum – which essentially is the product of mass and velocity. For example the displacement tonnage of 10,000 when multiplied by a speed of one knot has half the momentum when multiplied by a speed of two knots. The energy of impact is twice, thrice, four times and so on with every knot of increase of speed.

Now, when it comes to practice the speed always cannot be restricted to bare minimum, owing to certain conditions such as the tides, wind effects, tugs erratic pull, engine failures etc. A good marine fender system can save the day in such exigencies.

Ideally a marine fender system should be cost effective, with low maintenance cost and high durability. The material should be locally available should a case of replacement arise.

While berthing, the navigator of the ship has to consider the amount of berthing energy involved. It is actually a product of various variants such as mass of the vessel or displacement, it’s approach velocity, the added mass co-efficient ( which is the mass of the water that is moving along with the vessel and is suddenly stopped at the point of contact), the eccentricity factor which is the rotational movement generated by a reaction force when the bow or stern comes in contact with the marine fenders at the berth, the berthing configuration factor which is the amount of energy absorbed by the cushion effect of the water between the quay wall of the berth and the approaching vessel, and the softness factor which is the energy absorbed by the deformation of the ship’s hull and the shore marine fender.

Abnormal energy is the energy that exceeds the normal berthing energy when berthing is done in abnormal conditions such as inclement weather, during human or technical error or an ominous combination of all three.

To neutralize this kinetic force imparted by the ship on the pier or berth, some work must be done by the quay wall and the shore structure upon the hull of the ship.

The reactive force of the dock installations increases dramatically, immediately after the impact of the ship’s hull upon it. As a result both the hull and the dock structure deflect according to their respective stiffness.

Herein the marine fender, which is fitted in their interface, becomes active. It deflects and reduces the berthing energy drastically without causing permanent damage to the hull of the vessel or concrete of the berth.  Naturally fenders should have high force absorption capacity without exerting a reactive force upon the quay.

Types of Fenders

Now the question arises what is the type of fender to be used in a specific berthing of ship?

Marine fender selection is important as it determines the safety of the personnel, cargo and body of the ship and its equipments. The turn around time of the ship can depend on the quality of the fender. One has to keep in mind the statistics of the heaviest and the largest vessel that reports to the dock before selecting and arranging the marine fender system.

Hollow wooden fenders of yester years are now giving way to various types of rubber marine fender, foam marine fender and pneumatic marine fenders Now fixed rubber fender systems comes in different varieties such as

• Cone fenders
• Cell fenders
• Arch fenders
• Cylindrical fenders
• D type fenders
• Leg fenders
• Dock corner rubber fenders
• Pie-type rubber fenders

Foam fenders contain chemicals such as Ethylene Vinyl Acetate (EVA), which are floatable and low in maintenance cost. A polyurethane spray or elastic-polymer sprays are used over these fenders to create near total wear resistant exterior.

Pneumatic fenders are air filled floating marine fenders which can be fitted on quay wall or ships hull according to the requirement. There are four types of pneumatic marine fenders

• Sling type fender
• Rib type fender
• Rope net fender
• China and tyre net.

Fenders are an integral part of safety system of the ship which reduces the shocks upon the quay or the hull. A wide range or variety of marine fenders is available in the market for different applications. They are not only used for merchant vessels, but also for boats, yachts, and other floating vessels.

The right choice of the marine fender to optimize the cost and the effectiveness is a matter which requires experience and expertise, not to say a thorough overall knowledge of the available varieties, requirements and the theory that goes with it.

How Marine Fenders Are Used For Ship Berthing? appeared first on Marine Insight - The Maritime Industry Guide

Back in the old days of merchant shipping, the ‘Quarter Master’ was a vital member of the Bridge team. ‘Quarter Master’ was the title given to the able bodied seamen whose primary responsibility was to steer the ship according to the Master’s and Officer’s helm orders. Quarter Masters kept watches and took turns on the helm all day when at sea. This practise continued until automation took over in the field of navigation. The significance of Quarter Master almost vanished off when the revolutionary equipment ‘Auto-Pilot’ was invented.  It was during the early 1920’s when an automated steering and helm control system was introduced onboard merchant ships.

Auto-Pilot system is considered as one of the most advanced and technically sophisticated navigational equipment tools on ships. Auto-Pilot is synchronised with the Gyro Compass to steer manually input courses, with reference to the gyro heading. Auto Pilot steers the manually input course by controlling the steering gear to turn the rudder in the required manner. Furthermore, modern auto-pilot systems are capable of being synchronised with the Electronic Chart system (ECDIS) enabling to follow the courses laid out in the Voyage plan. This feature cuts out the need of manual course changes and alterations as the system will follow the courses and alterations as per the voyage plan.

Auto-pilot system is surely an undeniable boon in modern navigation. However over-reliance on the equipment and poor comprehension of its efficiency and limitations has resulted in several accidents at sea. This was also because of the inability of the operators to study the equipment beyond its basic features.

The below notes are a brief outline of 10 important points to be considered while operating Auto-pilot system onboard for safe and smooth navigation.

1. Rate of Turn and Rudder Limits

The method of turn is the most important control of the Auto-Pilot system. The system will use the selected turn method for course alterations. The user can input the limit of such turn methods, which are as follows

a. Rate of Turn 

This is the most commonly used turn method. In this method, the user can set a value of turn rate between 1-300 degrees (varies on different models). When turning, the rudder will move as much as it takes to attain the required turn rate without exceeding the set value.  The officer must consider the vessel’s manoeuvring characteristics and set a value safe for the vessel.

b. Rudder Limits

Rudder limit method allows the user to set a value from 1 degree to the max rudder angle. In this method, while altering course the rudder will not exceed more than the set limit. Again, the vessel’s manoeuvring characteristics should be considered while choosing the rudder value.

Modern systems allow turning by radius as well. In such method the user can input turn radius in nautical miles.

2. Steering Gear Pumps

Steering gear pumps are used to pump hydraulic oil to actuate the steering gear unit (RAM) which in turn moves the rudder in the required direction. That means, when more pumps are running, the rudder will move more swiftly. The number of pumps available varies as per the steering gear unit.

The officer of watch should be aware of the pumps and use it wisely.

If operating the auto-pilot in areas with traffic density where sudden and swift alterations are required, maximum steering gear pumps shall be running.

In ocean cruising and open sea navigation with less traffic, the pumps running shall be reduced to its minimum.

 3. Off Course Alarm

An off-course alarm serves for the purpose of notifying the operator if there is any difference in the set course and the actual heading of the vessel. The user can manually set the required amount of degrees, after which an alarm will sound to notify the user that the set degree of difference has exceeded.

However, the user has to keep a check on the course changes as in some cases when the gyro compass wanders its course, the auto-pilot will follow the wandering compass and fail to sound the alarm.

4. Manual Mode

The steering controls of the system can be categorised as Automatic and Manual mode. It allows the ship to be navigated either in Manual mode or Automatic mode by switching the controls.

In Manual Mode, the vessel can be hand steered by using the Follow-Up Helm or a Non-Follow up emergency tiller.

Hand steering is used when the ship is manoeuvring, and navigating in restricted waters, channels and areas with traffic density traffic density.

NFU tiller when used will move the rudder in a desired direction but not to a specific angle. This is used in case of emergencies.

The user must be familiar with the procedure of inter-switching from Auto and Manual modes.

5. Traffic Density

The use of Auto-Pilot is not recommended when navigating in areas with high traffic density, narrow channels and traffic separation schemes and other restricted waters. The auto pilot may not be efficient enough to turn the vessel spontaneously while navigating in such areas demanding swift alterations and manoeuvres to avoid a collision or close quarter situation. If the auto-pilot is used in such cases, all the steering gear pumps shall be switched on for better rudder response.

6. Speed

The system works inefficiently on reduced speeds. The use of the auto-pilot is not recommended when the ship is manoeuvring or steaming in very less speed.

The system allows the users to synchronise with the Speed Log to receive feeds on the ship’s speed. The users should keep a check on the speed log as any error in the log speed will reflect in the auto-pilot system.

The system also allows the users to manually input the speed, when doing so it is important to set a value as close as possible to the actual speed of the vessel.

7. Weather Conditions

Rough weather and hostile sea conditions have adverse effects on the performance of the auto-pilot. Uncontrolled yawing of the ship can result in excessive rudder movement. Modern auto-pilot system has Weather control option in which the system automatically adjusts the setting to adapt to the changing weather and sea conditions. It also provides an option for the user to manual set a specific value.

8. Gyro Compass

The Auto-Pilot system is functionally dependant on the Gyro Compass. If there is any error or fluctuation in the gyro heading, there will be an equivalent change in the course steered. In worse cases, when gyro fails, the system will lose track on its heading and will be unable to steer the required course.

In any case of emergency, power blackout or gyro failure the system should be immediately changed over to Manual mode and use the helm to steer the course using Magnetic compass.

9. Important Alarms and signals

Apart  from off course alarm, an auto pilot must be integrated with:

a. Failure or reduction in power alarm, which will sound in the event of auto pilot failure or in case when there is reduction in the power supply to heading control or monitoring system

b. Sensor status monitoring: If any of the sensors in the auto pilot system fails to respond, it should be indicated by an audible alarm in the monitoring system

c. Heading monitor: If the ship is required to carry two independent compasses, a heading monitor to track the current heading information by independent heading sources must be provided. An audio-visual alarm both to be provided if the heading information in use diverts from the second heading source beyond a set limit. It should also be provided with clear indication of actual heading source.

10. Important Limitations: The auto pilot system must be such that the preset heading cannot be altered by intentional intervention of onboard personal and the heading control system should change the course to preset heading without overshooting its position

As we have stated above, auto-pilot is an undeniable boon in modern navigation. It is the responsibility of the officers to ensure that they are completely aware of the equipment and its features and controls to make a proper and efficient use of it. Despite the fact that auto-pilot systems varies in model from ship to ship, it’s working principle and features will be the same. Deck officers making use of the equipment are strongly recommended to read the manufacture’s operating manual to get a thorough understanding of the equipment.

You may also like to read – An Insight into the Automated Guided Vehicle (AGV) Used in the Maritime Industry

Do you have more points to mention?

If so, we would like to see them as comments.

10 Things to Consider While Using Auto-Pilot System on Ships appeared first on Marine Insight - The Maritime Industry Guide

The development of GMDSS (Global Maritime Distress And Safety System) for the shipping industry has come a long way. The GMDSS system was established with an objective to improve distress and safety radio communications and procedures at sea.

The greatest benefit of the GMDSS equipment is that it vastly reduces the chances of ships disappearing without a trace, and enables search and rescue (SAR) operations to be launched without delay and directed to the exact site of a maritime disaster.

Gone are the days when ships were required to have dedicated radio officers to operate radio equipment. With the implementation of GMDSS, every deck officer with a General Operator Certificate (GOC) and the license is entitled to use the GMDSS equipment and make radio communications when needed.

For the GMDSS equipment to function properly and effectively in the event of an emergency, it is critical that mariners understand its purpose and do the required maintenance on board the vessel to keep it in a working condition and make the best use of GMDSS equipment.

The daily, weekly and monthly tests of all the GMDSS equipment should be done by every navigating officer responsible for it without any compromise. We must not forget that it is our only best friend in a distress situation at sea.

Ships at sea must be capable of performing the nine functional GMDSS requirements. They are:

1. Ship-to-shore distress alerting
2. Shore-to-ship distress alerting
3. Ship-to-ship distress alerting
4. SAR coordination
5. On-scene communications
6. Transmission and receipt of emergency locating signals
7. Transmission and receipt of MSI
8. General radio communications
9. Bridge-to-bridge communications

This can be ensured by testing the GMDSS equipment at regular intervals.

The GMDSS equipment and systems include the VHF DSC/RT, MF/HF DSC/RT, INMARSAT, SART, EPIRB, NAVTEX, and SURVIVAL CRAFT TWO WAY VHF.

Daily Tests On GMDSS Equipment

The proper functioning of the Digital Selective Calling (DSC) facilities shall be tested at least once each day, without radiation of signals, by the use of the equipment’s Internal test facility. The daily test checks the internal connection, transmitting output power and the display. The process can differ from equipment to equipment based on the make.

The daily test of the FURUNO model of the VHF equipment can be executed as below:

1. At the standby display press, the SHIFT key followed by the TEST key. The “TEST IN PROGRESS” pop up window appears momentarily and distress alarm both visual and audible occurs.

The display shows the TEST screen. If everything is okay with the set and is functioning properly, the results show OK as below. However, in some situation or if it’s a faulty equipment, ‘NG’ may be displayed. In this case the daily test should be repeated a couple of times. If the problem persists, it should be immediately brought to the notice of a shore based service engineer.

2. Press the CANCEL key to stop the alarm. To stop the daily test, press the CANCEL key again.

Daily test also needs to be performed on the MF/HF equipment to ensure it will function properly in the event of distress.

1.  Press the [3/TEST] key to start the test. Select the Daily Test by rotating the knob and push to enter. After several seconds the display shows the test results; OK for normal operation. The audio alarm also sounds after the test results are displayed and the alarm lamp flashes several times.

2. The CANCEL key should be pressed to quit the test and return to the normal screen.

Batteries providing a reserve source of energy should also be checked daily. Mainly the battery ON-LOAD and OFF-LOAD voltages are checked by a voltmeter connected to the charger.

OFF-LOAD: when no equipment is connected, the battery should read 24 V or slightly more.

ON LOAD: switch off the AC power and note the voltage of the battery. Press the PTT on MF/HF transceiver on a non-distress and idle R/T frequency. Voltage will fall depending upon the load. If the voltage falls more than 10% it indicates that the battery is either weak or not charged fully. In this case, batteries should be recharged.

It is also important to check that all printers are in a working condition and there is sufficient supply of paper.

Weekly Tests On GMDSS Equipment

It is necessary to test the proper operation of the DSC facilities at least once a week by means of a test call over one of the six distress and safety frequencies, when within the communication range of a coast station fitted with a DSC equipment. A test call to the coast station can be sent in the following ways:

MF/HF DSC:

1.  Press the [2/DSC] key at the DSC standby screen and then push the [ENTER] knob to open the CALL TYPE menu.

2. Rotate the [ENTER] knob to choose TEST CALL and then push the [ENTER] knob. Push the [ENTER] knob again to open the COAST ID menu.

3. Using the numeric keys, key in the ID of the coast station ID (seven digits) where you want to send the call depending upon the area you are navigating in and then push the [ENTER] knob. The coast station ID can be found from the Admiralty List of Radio Signals Volume 1- Maritime Radio Stations.

4. Now push the [ENTER] knob to open the DSC FREQ menu. (Note that here the PRIORITY is automatically selected to SAFETY.)

5. Rotate the [ENTER] knob to choose an appropriate frequency and then push the [ENTER] knob.

6. Now press the [CALL] key to send the TEST call to the respective shore station.

After the test call has been sent successfully the acknowledgement is received from the shore station. The audio alarm sounds on receiving the acknowledgement.

Many times it often happens that the deck officer does not receive any acknowledgement from the shore station. In such cases, we often take it for granted that the shore station is not sending the acknowledgement. However, in reality, this might not be the case.

The problem could be with our equipment too. To make sure that the MF/HF equipment is in order, it is better we try sending the test call using other frequencies and to other stations. Even if then we fail to receive any acknowledgement, a test call can be sent to a passing ship if possible. Instead of keying the coast ID, key in the MMSI of the passing ship. It is better to call the ship and confirm if they have received the test call. We can also request them to send us a test call to ensure that the equipment receiving facility is functioning properly.

It is also recommended that a station to station test takes place using VHF DSC.

1. Press the CALL key. This will open the compose message screen where the call type can be selected. Rotate the channel knob to select TEST call.

2. Enter the Station ID, in this case, the MMSI of your own ship and then press the CALL key for it to be transmitted.

The audio and visual alarm is generated and the test call is received on the other VHF station. Press cancel to terminate the test call.

Monthly Tests On GMDSS Equipment

EPIRB:

The Emergency Position Indicating Radio Beacon or EPIRB should be examined by carrying out a self-test function without using the satellite system. No emergency signal is transmitted during the self-test. During self-test the battery voltage, output power and frequency are checked. The EPIRB should also be checked for any physical damage. The expiry date of the battery unit and that of the hydrostatic release unit should be checked. Also, check that the safety clip is properly attached and in place.

To perform the self-test on the JOTRON EPIRB:

1. The EPIRB should be removed from the bracket first.

2. The spring loaded switch on top of the EPIRB is then lifted to the TEST position.

A successful test will consist of a series of blinks on the LED test-indicator, followed by a continuous light and a strobe flash after approximately 15 seconds. The last green led indicates a successful test.

3. After the successful completion of the test, the switch is released and the EPIRB is put back into the bracket.

SART:

The Search and Rescue Transponder or SART is also equipped with a self-test mechanism to test the operational function of the beacon. The SART is tested using the ship’s X band radar. The test should preferably be done in open seas to avoid interference on the radar display.

1. Remove the SART from the mounting bracket.
2. The SART should be held by one person in view of the radar scanner. This could be done from the bridge wings. The SART should then be put on the TEST mode by rotating it to the left to the TESTPREVUE position for a brief period.

Visual lights operate and bleeps are heard indicating that the SART has been triggered.

3. Simultaneously a person should observe the radar display for the correct pattern. At least 11 concentric circles appear on the radar display if kept on a 12 M range scale. The distance between the two rings is approximately 0.64 NM.

4. The SART should also be visually inspected for any signs of physical damage. The battery expiry date should also be noted. The safety clip should be in place.

Survival Craft Two Way Portable VHF Equipment

Each survival craft two way VHF equipment should be tested at least once a month to ensure proper operation in case of a distress situation. It should be tested on a frequency other than VHF channel 16 (156.8 MHz). The expiry date of the battery needs to be checked and changed when required.

1.  Press the power key to switch on or off.

2.  To select a different channel, press the CH key and use the arrow keys to select the required channel. The selected channel is indicated with channel number and frequency on the screen.

3.  Press the PTT (Push to talk) to communicate with another radio-telephone to test receive and transmit functions. One person can stand near the VHF receiver to receive a test call from the handheld radio.

The symbol ‘TX’ is shown when the PTT is pressed and transmission takes place. The TX indicator indicates that a carrier is produced at the antenna output.

When it receives a signal the symbol ‘RX’ is indicated on the display.

NAVTEX :

The Navtex is an equally important GMDSS equipment and is the source of maritime safety information. It is also equipped with a test function that can test the battery, keyboard, LCD, ROM and RAM. It is a good practice to test the Navtex and detect an error if any. The Furuno model of Navtex can be tested as follows:

1. Press the MENU/ESC key to open the main menu.

2. Now use the navigating arrows to choose SERVICE and then hit ENT. The SERVICE submenu contains the TEST option. Use the down arrow key to select TEST and press ENT key. Choose YES and press the ENT key again. The TEST will start and the results will be displayed on the screen after a few seconds.

If the test is successful the results show OK otherwise it will show NG meaning – No Good.

It also tests each key for proper functioning.

The Rx test screen shows as follows:

The test results can be printed and filed in the GMDSS log book.

INMARSAT:

The INMARSAT is also equipped with a diagnostic test which checks it for proper operation. The steps to perform a Diagnostic Test on FURUNO INMARSAT are given below;

1. On the keyboard press the F7 key to display the ‘OPTIONS’ menu.
2. Use the down arrow to open the TEST menu and then select the DIAGNOSTIC TEST. Select YES to begin the test.

On completion of the test, the results are shown on the screen as below. The ESC key is used to return to the main menu.

A PV test or Performance Verification test can be performed every month. This test consists of receiving a test message from an LES (Local Earth Station), transmitting a message to an LES and a distress alert test. The PV TEST can be opened from the TEST menu under OPTIONS as mentioned above.

The status shows ‘TESTING’ when the test is in process.

The status changes to IDLE on completion of the PV Test.

The test results can be seen from the option ‘PV Test Result’ under the TEST menu. The test results can be printed and logged. BBER denotes the bulletin board error rate. Pass appears for no error. “PASS” appears for satisfactory completion of the test.

GMDSS Battery:

The battery connections and compartment should also be checked. The level of the electrolyte and the specific gravity of each cell should be checked and recorded. Sulfation can reduce the specific gravity thereby reducing the battery capacity. Maintenance free batteries on board, however, do not require any such checks.

It is recommended every month to visually check all antennas for the security of mounting and visible damage to the cables. The antennas are located on the monkey island. Any deposit of dirt and salt should be removed. It is also important to check the condition of the aerials and insulators along with the help of an electrical officer. Ensure that the equipment is switched off and isolated before carrying out any work on the antenna.

GMDSS enables a ship in distress to send an alert using various radio systems. It is therefore important that all the GMDSS equipment are maintained in a state of readiness and working condition. To achieve this it is mandatory to perform the daily, weekly and monthly tests. Only then can we ensure the safety of the ship and its crew.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

Daily, Monthly And Weekly Tests Of GMDSS Equipment On Board Ships appeared first on Marine Insight - The Maritime Industry Guide

Note: This is the first article in the ship navigation series by the very experienced Captain Ashish Joshi. 

RADAR (radio detection and ranging) equipment has for a long time been one of the best tools for enhancing the safety of ship navigation at sea. Gone are the days when the master would be the one switching the equipment “on” and “off”, at his/her discretion, and when old timers would sneer at a young officer on seeing him use the RADAR. If the radar was fitted with a capable ARPA it was a real luxury on the navigation bridge of the vessel.

Thanks to the manufacturers, IMO performance specifications and regular feedback from the maritime fraternity the equipment itself has become user-friendly. Technology has improved immensely and the end product is nowhere near to the original equipment that required manual plotting techniques sheets and chinagraph pencils that tested the patience of the navigators and made it difficult to track multiple targets simultaneously.

Almost all radars today are fitted with an ARPA (automatic radar plotting aid), therefore when not being used for coastal navigation, the radar is mainly used for collision avoidance.

Regulations for proper use for collision avoidance are mentioned in COLREGS rules 6,7,8 and 19; where rule 5 says that all available means must be used for keeping a proper lookout and that includes the use of radar. Rule 9 requirement to keep as near as possible to the starboard side of a narrow channel or fairway would also necessitate the use of radar.

Related Reading: 15 Things To Consider While Using Radar On Ship

Few items are now being discussed regarding the use of radar and this list is by no means exhaustive:

1. Conditions at sea are ever-changing on the basis of weather conditions and vessel traffic density, and therefore a navigator should adjust radar setting to her requirements and regularly monitor the settings throughout the watch; this is commonly referred to as tuning the radar. For example, if it was raining during Chief Mate’s watch and the sky is clear during your watch, you definitely don’t need to apply rain clutter. This is applicable for other radar controls too. Not many navigators are aware of this, but improper use of clutter controls can mask targets or hamper their tracking. Similarly, range scale would depend on traffic condition and type of traffic being encountered as well as on your own ship’s speed.

Some radars have settings preset depending on the type of the situation and expected use, make sure that you are aware of such settings. It is fine if such presets have names, however, be careful in case they have numbers, e.g. Picture 1 on your previous ship’s radar may not be same as Picture 1 on your present ship’s radar.

2. Ship owners generally have uniformity in equipment on all ships across the fleet; this is great if you sail on these kinds of ships. If not then ensure that you are well familiarized with the equipment prior taking over your first watch you. Get all the information so that you are confident during your watch. Information can be obtained from your predecessor, other navigators or the user manual.

Like all marine navigation electronics, radar can also fail and you will need to know how to reset the equipment when needed. Nowadays we don’t have radio officer, or sometimes not even electrical officer at sea. You must know where radar spare parts are stored and be ready do some minor maintenance like changing the magnetron.

3. Another setting to be careful about is the speed input into the radar. As we all know COLREGS pay emphasis on the aspect of the vessel for ascertaining the risk of collision and required action to be taken. This needs ships’ speed through water (STW) by log input. Here is a look at the correct setting for collision avoidance using STW.

This would be great if the only job on the bridge was collision avoidance. But there is also a need for situational awareness during coastal navigation and for ascertaining set and drift speed through the ground is needed via GPS input. Improper monitoring of a vessel at this critical time has been the root cause of several collisions and allisions even by experienced ship handlers.

Here is a look at setting on the radar with speed over ground setting (SOG) by GPS input.

Both the pictures above were taken about 15 seconds apart and a navigator should be able to differentiate between the two radar pictures and also appreciate the need for using both the settings as situation demands.

You can also see that log speed will give the illusion that the vessel will pass to the south of VAIS (Virtual Automatic Identification System), whereas GPS speed gives actual information as evident from the vector that vessel will pass North of VAIS.

Related Reading: Important Points Officer Of Watch Must Consider While Using Ship Radar

4. A word of caution is required here in view of safety of the vessel; situations can change and develop rapidly when in coastal waters or areas of dense traffic, bridge team must be made aware whenever a navigator is changing settings. Also if you are a junior navigator in the team, revert the settings back to original immediately after making your observation.

This information regarding change of settings must also be borne in mind when a radar is being used by a pilot, do not change the settings as they may not be completely familiar with all aspects of your equipment and can get confused or disoriented when seeing a different picture than what is expected or they are used to.

5. Most of the bridges will be fitted with at least two marine radars and generally one of them will be X-band radar and the other will be S-band radar. Make sure that you know the difference between the two and what settings are suitable according to the situation. It is not wise to be navigating with two radars and using same range scale on both.

Many times it so happens that navigators are comfortable conning a vessel from a single location and this leads to over-dependence on one radar even when the other radar is much more suitable for the situation at hand.

Generally, due to operating frequency X band radar provides a clearer viewing screen and is used for target detection and collision avoidance. Whereas S-band radar gives better picture because it’s radio waves can penetrate through fog particles and rain.

• Proper Use Of ECDIS Safety Setting On Ships
• Important Points For Dealing With Navigational Warnings On Ships
• NAVTEX On Ships
• Pros and Cons Of ECDIS

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

5 Effective Radar Techniques for Ship Navigators – Part 1 appeared first on Marine Insight - The Maritime Industry Guide

A Gyro compass is a form of gyroscope, used widely on ships employing an electrically powered, fast-spinning gyroscope wheel and frictional forces among other factors utilising the basic physical laws, influences of gravity and the Earth’s rotation to find the true north.

Construction

Gyro compass has become one indispensable instrument in almost all merchant ships or naval vessels for its ability to detect the direction of the true north and not the magnetic north. It is comprised of the following units:

• Master Compass: Discovers and maintains the true north reading with the help of a gyroscope.

• Repeater Compasses: Receive and indicate the true direction transmitted electrically from the Master Compass.

• Course Recorder: Makes a continuous record of the manoeuvring on a moving strip of paper.

• Control Panel: Governs the electrical operation of the system and ascertains the running condition by means of a suitable meter.

• Voltage Regulator: Maintains constant supply of the ship to the motor-generator.

• Alarm Unit: Indicates failure of the ship’s supply.

• Amplifier Panel: Controls the follow-up system.
• Motor Generator: Converts the ship’s DC supply to AC and energizes the Compass equipment.

Gyro compasses are linked to the repeater compasses via one transmission system. The fast-spinning rotor attached weighs from 1.25 pounds to 55 pounds.

It is driven thousands of revolutions per minute by another electric motor. However, the most essential part of a Gyro compass system is the spinning wheel, which is known as the Gyroscope.

Working

External magnetic fields which deflect normal compasses cannot affect Gyro compasses. When a ship alters its course the independently driven framework called ‘Phantom’ moves with it, but the rotor system continues to point northward.

This lack of alignment enables it to send a signal to the driving motor, which moves the phantom step in with the rotor system again in a path where the phantom may have crossed only a fraction of a degree or several degrees of the compass circle.

As soon as they are aligned, electrical impulses are sent by the phantom to the repeater compasses for each degree it traverses.

The Gyroscope in the Gyrocompass is mounted in such a way so that it can move freely about three mutually perpendicular axes and is controlled as to enable its axis of spin settled parallel with the true meridian, influenced by the Earth’s rotation and gravity.

The Gyrocompass system applications are based upon two fundamental characteristics, which are:

• Gyroscopic Inertia: The tendency of any revolving body to uphold its plane of rotation.

• Precession: A property that causes the gyroscope to move, when a couple is applied. But instead of moving in the direction of the couple, it moves at right angles to the axis of the applied couple and also the spinning wheel.

These two properties and the utilization of the Earth’s two natural forces, rotation and gravity, enacts the Gyrocompass to seek true north.

Once settled on the true meridian the rotor indefinitely will remain there as long as the electrical supply of the ship remains constant and unaltered and unaffected by external forces.

Usage and Errors

Gyro compasses are pre-eminently used in most ships in order to detect true north, steer, and find positions and record courses.

But due to the ship’s course, speed and latitude, there could appear some steaming errors. It has been found that on Northerly courses the Gyro compass north is slightly deflected to the West of the true meridian whereas on Southerly courses it is deflected to the East.

Modern ships use a GPS system or other navigational aids to feed data to the Gyrocompass for correcting the error. An orthogonal triad of fibre optic design and also ring laser gyroscopes which apply the principles of optical path difference to determine the rate of rotation, instead of depending upon mechanical parts, may help eliminate the flaws and detect true north.

You may also like to read-Automatic Identification System (AIS) & The Importance of Vessel Tracking System

An Introduction to Fluxgate Compass 

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

Gyro Compass on Ships: Construction, Working, and Usage appeared first on Marine Insight - The Maritime Industry Guide

Today, piloting in restricted waters has become a highly specialized job aided by modern technology. Gadgets, instruments and software tools are always in the process of evolving as newer advancements in the navigation aids and technology take place.

Gone are the days when one had to anchor during mist, fog or blizzards when visibility comes down to almost zero. Also, gone are the days when one had to take a position fix taking into consideration the external reference points across the navigating channels and plotting lines using a bearing indicator.

The point of intersection of the lines on the chart used to give the position of the vessel. The point of intersection was called fix. Today, GPS, or a space assisted “Global Positioning System” has taken over and has virtually become indispensable for any sort of aerial, land or marine navigation. Moreover, new advanced control systems, which offer higher accuracy and integrity to the GPS, are always in the process of development to bolster the existing positioning system. Every ship today uses several navigational equipment tools for utmost safety.

Previously navigators used to depend solely upon nautical charts, which were actually plotted on papers and were the official database of the government authorized hydrographic departments. Those charts used to give a two dimensional view of the sea or river bed and its topography to assist safe navigation.

Charts also indicate navigational hazards, sudden elevations on the sea bed, wrecks that block the navigation channel in restricted water, any kind of local man-made structures, position of the bridges, ports, structures on shore, position of the guiding buoys, turrets, obelisks and other shore references. These charts were prepared by the hydrographic departments and were updated after certain gaps, which made navigation vulnerable to sudden changes on the sea bed of the channel.

Physical charts also used huge space block in the chart room on the bridge where charts were placed. To avoid this Electronic Nautical Charts were developed to move on from the paper to the digital variety.

There are two main types of ENCs, the raster chart and the vector chart. While the first is merely a scanned variety of the earlier paper navigational charts discussed, the second is more data oriented. Though they are hidden, the data at a particular position are instantly given when sought for (with a click of the mouse or pressing a button). This disclosure is achieved when the ENC is customized by the navigational software, like ECDIS or Electronic chart Display Information System.

All the electronic nautical charts conform to the guidelines of International Hydrographic Organization. Moreover, these charts are regularly updated according to the resolution adopted by the IMO which invited governments of member countries to conduct hydrographic surveys and publish and disseminate nautical information for safe navigation. The member governments should coordinate amongst themselves, wherever necessary, to timely update the information and ensure greatest possible uniformity in the published charts.

Numerous chart plotting software also exist in the market which can be quite handy for navigation. One such is SEA CLARE, which is pc based software for windows 2000 and above. When connected to GPS, it shows current position, speed and heading of the vessel in real time. New charts can be fed automatically in text file and tracks can be saved for later viewing. Entries can be manually updated and entered. Numerous waypoints can be created to assist navigation. The GPS transmission capability must however be of a bit modern version called NMEA 0183 (which is a specification or protocol developed by The National Marine Electronic Association, Maryland, USA).

Other bridge instruments which conform to this protocol can be connected to have various data on the screen along with the chart. Data like depth of water below keel, wind direction, ship’s heading from gyro, and even AIS can be connected to locate nearing vessel movements.

A simpler version called PC PLOTTER is generally used by smaller crafts for yachting, fishing, and is fitted with a low cost Dual Channel Parallel AIS Receiver which can receive signals from large and small ships.

AIS is the vessel tracking system to locate other ships in the vicinity by automatically exchanging data with nearby ships and AIS base stations. Local VTMS (Vessel Traffic Management Systems) / VTS (Vessel Traffic Service) is offered by ports where traffic is pretty busy but here the AIS acts as an additional supporting instrument. More details about AIS can be found here.

Another instrument that reduces the work load of the officer on watch and pilots is the marine RADAR fitted with ARPA. Radar, as we all know is a Radio Detection and ranging device that is capable of reflecting electromagnetic wave. Ships, aircrafts, buildings, motor vehicles, marshy lands, water body, low lying cloud chunks all reflect radio waves and hence are visible on the screen. The ARPA can calculate the speed of the tracked vessel, its course and forecast the closest point of approach. Relative speed between the vessel and a static point like a land mass can be calculated, and collision point and time indicated. Modern integrated ARPA has replaced the initial stand-alone with better end result for the captain and his staff.

Maris, a Norwegian company, has another chart system based on ECDIS called Pilot Mate, which integrates with the bridge gadgets quickly. Here real time update for available drafts is received over email and so is tidal information, display of real color guiding ENC buoys, update history management etc. Route planning and monitoring are added advantages of this system.

Thus we see that chart work with dividers, set-squares, sextant, and other tools have given way to a more digital environment on the bridge, thus almost eliminating the chances of human error. A truly digitally integrated system on the bridge virtually eliminates the chances of being aground or getting completely lost at the sea.

What Marine Navigation Systems and Electronic Tools Are Used by Ship’s Pilot? appeared first on Marine Insight - The Maritime Industry Guide

It is of utmost importance that every navigating officer ensures the safety of the vessel and its crew. Accidents can happen to the most cautious and prudent of navigator.

Right from the start of voyage planning, the navigator needs up to date information that will affect the passage of the ship. The most important information to vessels is information related to safety including Maritime Safety Information.

Maritime Safety Information includes navigational and meteorological warnings, meteorological forecasts, warnings about dangers to navigation, warnings of missing vessels and other urgent messages pertaining to the safety of the vessel and its crew.

Constant monitoring to pick up wanted information among a vast volume of messages is not very practical with a limited radio system. The NAVTEX system provides all navigating officers with up to the minute information automatically.

NAVTEX, an acronym for navigational telex (navigational text messages) is a device used on-board the vessels to provide short range Maritime Safety Information in coastal waters automatically.

It can be used in ships of all types and sizes. The area covered by Navtex can extend as far as 400 nautical miles from the broadcast station. A NAVTEX receiver onboard prints out navigational and meteorological warnings and forecasts as well as urgent Marine Safety Information to ships.

It forms a vital element of the Global Maritime Distress Safety System (GMDSS). Navtex uses the feature of radio telex or Narrow Band Direct Printing (NBDP) for the automatic broadcast of information.

HOW NAVTEX WORKS?

The Navtex works on a frequency of 518 kHz in the medium frequency band. 490 kHz frequency is also used by some countries for broadcasts in the national languages, also known as national navtex.

Where medium frequency reception is difficult, transmissions are made on 4209.5 kHz. The default setting in a Navtex is 518 kHz. The entire world is divided into 21 areas known as NAVAREAS (including 5 areas recently introduced for the Arctic region) for the purpose of distributing this information.

Each Navarea has multiple navtex stations which further helps in transmitting the messages.

SELECTION OF STATIONS

All navtex receivers are programmable to enable the navigating officer to ensure that only messages from selected Navtex Stations are displayed or printed.

The SELECTING STATION menu under the Menu option in a Navtex Receiver allows the officer to select the desired stations he/she wants to receive automatically or manually.

On automatic selection, the navtex receives Marine Safety Information for the area the ship happens to be in continuously and without any user involvement.

If a ship’s position data is fed from any navigating equipment like GPS, the Navtex will automatically decide in which NAVAREA the ship is navigating presently and thus select the appropriate Navtex Stations.

In the manual mode, the navigating officer can select what stations he/she wishes to receive.

A list of Navtex Stations can be found in the Admiralty List of Radio Signals Volume 3 Part 1 and in the List of Coast Stations and Special Service Stations (List IV) for reference.

TYPES OF MESSAGES

The Navtex receives the following kind of messages:

A= Navigational Warning

B= Meteorological Warning

C= Ice report

D= Search and Rescue Information/ piracy and armed robbery

E= Meteorological forecast

F= Pilot messages

G= AIS messages(formerly Decca messages)

H= Loran C messages

I= Omega messages

J= Satnav messages (GPS or GLONASS)

K= Other electronic navigational aid system messages

L= navigational warnings (additional)

M to U= Reserve

V= Notice to fisherman

W to Y= Reserve

Z= No messages on hand

The navtex receiver can be set to ignore certain types of messages, however, messages A,B,D and L because of their importance cannot be rejected by navigating officers.

Audible alarms can also be generated when message type A,B,D or L is received. It should only be possible to reset this alarm manually.

We should also note that when programming the type of messages to receive, it is wise to ensure that only those which are required and necessary are programmed for the reception.

Otherwise, a good deal of paper will be wasted or one will have to scroll through a mass of messages if the broadcasts are received in soft copy.

THE FORMAT OF THE MESSAGE

The message in a Navtex Receiver appears in the following format:

ZCZC   b1 b2 b3 b4     MAIN MESSAGE     NNNN

ZCZC: It is the start code. It indicates the beginning of the message.

B1: This character represents the Station ID.

B2: This character is called the Subject Indicator. It is used to represent the type of message. (A to Z)

The characters B1 and B2 are used by the navtex receivers to reject messages from stations of concerning subjects of no interest to the officer.

B3 and B4: B3 and B4 is a 2 digit serial number for each message.

NNNN: This indicates the end of the message.

The characters B3 and B4 are used by receivers to keep already received message from being repeated.

Below is an example of a message:

ZCZC OA20

WZ 1593

Scotland, West Coast

The North cardinal light buoy 58.01.2N 005.27.1W

have been permanently withdrawn.

Cancel WZ 1562

NNNN

Every Navtex message has information within the message header. In the above message:

The letter “O” indicates a broadcast from the Navtex station, here Portpatrick radio.

“A” indicates a Navigational warning category message.

‘20’ indicates the navigational warning message priority sequence.

ADVANTAGES OF HAVING NAVTEX ONBOARD THE SHIPS:

Navtex is a form of extra insurance and aid in the peace of mind. It is a very convenient way of monitoring navigational warnings, meteorological warnings, search and rescue information and other data for ships sailing within 200 to 400 nautical miles off the coast. It thus provides pertinent navigational and weather-related information in real-time.

As Navtex receiver receives messages automatically it is quite a user friendly. An officer of the watch does not have to monitor it regularly or be physically present at a fixed time.

There is also no requirement for retuning of the receiver. This not only saves time but also stops an officer from being distracted on the bridge.

With the information received from the Navtex receiver, passage plan can be amended as required for the safety of the vessel.

An officer of the watch can attend to any distress warning in the vicinity. He is also aware of the expected weather and can plan accordingly. Thus a Navtex forms an integral part of the bridge navigational equipment.

NAVTEX RECEIVER CHECKLIST

1. Every officer should make sure that there are sufficient rolls of Navtex paper available onboard at all times.
2. It is important to check that there is paper in the receiver so that one does not miss out any important messages.
3. It is advisable to leave the Navtex ON at all times to avoid the chance of losing vital information that might affect the vessel during its voyage.
4. Make sure that the operating manual is available on the bridge.
5. A plastic copy of the NAVAREAs/METAREAs in which the vessel is likely to sail, showing the Navtex stations, their coverage ranges and their respective time schedules should be made available next to the equipment.
6. A handy guide for programming, status and auto testing procedures can be made and kept with the equipment.
7. Routine tests should be carried out to check the performance of the equipment.
8. Extra care should be taken not to confuse the programming of B1 characters (station designators) with those of B2 characters (type of messages).

Navtex is mandatory to be carried by all SOLAS approved vessels. It is small but powerful equipment. It provides safety information that can be tailored as per one’s particular needs.

Over to you..

Do you know any other important points on NAVTEX that can be added to this article?

Let’s know in the comments below.

NAVTEX On Ships: Working, Types Of Messages And Advantages appeared first on Marine Insight - The Maritime Industry Guide

The radar is one of the most used equipment systems onboard ships. It is designed for detecting and tracking targets a considerable distance. Needless to say, it’s of great practical value to the navigators.

Proper use of radar and radar plotting aids in both restricted visibility and clear weather can help prevent collisions and ensure the safety of the ship. Accidents can occur if the watch keeping officer is not fully conversant with the operation of the equipment. For reliable interpretation, it is essential that the radar operating controls be adjusted properly.

In this article, we would like to discuss how to interpret and understand a radar screen display. Below attached is a picture of a radar screen and the keyboard. This article will help to understand the basic approach to the use of marine radar.

1. CHOICE OF RANGE SCALE: Appropriate range scales should be used depending on the prevailing circumstances and conditions of the environment the ship is in. Where two radars are used, one radar can be kept on a longer range scale to obtain advance warning of the approach of other vessels, changes in traffic density, or proximity to the coastline. The other radar can use a short range scale, which helps to detect smaller targets easily. Use the RANGE key in the keyboard to select the range desired. The ‘+’ key increases the range whereas the ‘-’ key decreases the range.

The range scale shown in the picture below is 6 miles and each fixed range ring is pre-determined at an interval of 1 mile.

2. RANGE MEASUREMENT: Measurement of range to a target can be achieved either by the fixed range rings or the Variable Range Marker (VRM). The fixed range rings appear on the screen with a pre-determined interval depending upon the range scale in use and provide a rough estimate of the range to a target. The current interval is shown in the upper left position on the screen. Count the number of rings between the center of the display and the target to measure the range to a target. The Variable Range Marker’s diameter can be increased or decreased so that the marker touches the inner edge of the echo of the target thus giving more accurate range measurements. There are two sets of VRMs available and they appear as dashed rings. Press the VRM ON key to display either of the VRMs.

3. BEARING MEASUREMENT: Electronic Bearing Lines is used to take the bearing of targets. The EBL extends from the own ship position to the circumference of the radar screen. If bearing remains constant with decreasing range, the risk of collision exists.

4. GAIN: The gain control on the keyboard is used to adjust the sensitivity of the radar. It should be so adjusted that the background noise is just visible on the screen. In simple words, if the gain is set too low, weak echoes may be missed while excessive sensitivity yields too much background noise. Echoes from two targets on the same bearing can appear as a single pip on the PPI or the radar screen. A reduction in the gain setting is therefore required in this situation.

5. REDUCING SEA CLUTTER / RAIN: If rain or sea clutter is set too low, targets will be hidden in the clutter whereas if set too high can cause targets to disappear from the radar screen. The radar can also detect rain, snow or hail clutter in the same manner as normal targets. The A/C RAIN and A/C SEA control is used to adjust the rain and sea clutter respectively. The scroll wheel is rolled clockwise or anticlockwise to increase or decrease the clutter.

6. OF CENTRE DISPLAY: Own ship position can be displaced to expand the view field without switching to a large range scale. However while doing so care should be taken that at least one mile of viewing range is kept on the aft of the ship to view targets on the ship’s aft or ships trying to overtake own vessel. The cursor can be put to the position where you wish to move the ship’s position and then press the OFF CENTRE key on the keyboard.

7. TARGET TRAILS: Target trails can be of great assistance to the radar observer in making an early assessment of the situation. The trail can either be relative or true. Relative trail shows relative movement between own ship and target. True trail presents true target movements depending on their over the ground speed and course. Relative trails give an early indication if a close quarter situation is developing or risk of collision exists. Relative trails when combined with true vectors gives an indication of the relative movement of other vessels and the risk they present. The trail time can be adjusted as per requirement.

8. PI (PARALLEL INDEX) LINES: This is a useful method of monitoring cross track tendency. It helps us to assess the distance at which the ship will pass a fixed object on a particular course. The index line is drawn parallel to the planned ground track and should touch the edge of a radar echo of a fixed object, at a range equal to the desired passing distance. Any cross track tendency (such as caused by a tidal stream, drift or current) becomes apparent as the target moves off the parallel line. This technique can be used in both relative and true motion. Use the trackball to select the PI line number box. Select a PI line number and push left button to turn it off or on. Roll the scroll wheel to adjust the PI line orientation (between 000°T to 359.9°T).

9. HEADING/SPEED/COURSE: The top right corner of the radar screen display shows the heading, speed, course, and speed over the ground, own ship position, and the source. Speed can be entered from a log(STW) or GPS(SOG) or manually.

Speed over the ground (SOG) IS the speed of the vessel referenced to the surface of the earth. Speed through the water (STW) is the speed of the vessel referenced to the water in which it is navigating. In general, STW is used for radar collision avoidance to provide a more accurate indication of the target’s aspect and SOG is used for navigation. Right click the speed box to select the source for speed.

Right click the own ship position box to select the source of position data- GPS1/2 or DEAD RECKONING.

10. BRILLIANCE: The overall brilliance of the screen can be adjusted according to lighting conditions using the BRILL KEY by turning clockwise or anti-clockwise. The brilliance box at the bottom left corner of the screen provides various palettes and other options as shown below. Select the item needed and roll the scroll wheel to adjust the brilliance. The brilliance menu can be seen by right-clicking on the brilliance box.

11. WATCH ALARM: the function of the watch alarm is quite similar to that of BNWAS. The watch alarm sounds the audio alarm at selected time intervals to help keep regular watch of the radar picture. The countdown starts from the value set. Officers often need to spend time inside chart table thus sometimes forgetting to keep a radar watch. Watch alarm can, therefore, be used to avoid being occupied for a long time inside radio room or chart room. The ALARM 1 and 2 in the picture below is used to set up the alarm. The ALARM ACK key should be pressed to silence the alarm.

12. VECTOR MODE: target vectors CAN BE SET relative to own ship’s heading (RELATIVE) or North (TRUE). When determining close quarter situation or risk of collision exist use of relative vectors is preferred. It is a good practice to switch between true and relative vectors to gain a better appreciation of the navigational situation. When using a true vector, own ship and other ship moves at their true speed and course. True vectors can distinguish between moving and stationary targets. The relative vector helps to find ships on a collision course. A ship whose vector passes through own ship’s position is on a collision course. The Vector Length can be adjusted to the required time frame. It is useful to have both relative and true information visible simultaneously; this can be achieved by selecting relative vectors with true trails. Combining true vectors with true trails will give no indication of the relative movement of other vessels and the risk they present. Shift the cursor to vector mode box and left click to select the vector required. The vector time can also be selected using the left button.

In the picture above, the vector mode is relative and trail used is true.

12. PAST POSITION: The past position Is a useful indicator. These history dots are placed at a fixed preset interval. Dots in a straight line at even spacing indicate a steady course and speed by the targets. Any changes can be noted as the spacing becomes uneven. Change of course will not be shown in a straight line. A curve in the trail indicates an alteration of course whereas the change in the spacing of the plots indicates a change in the speed of the target. The past data can also help the observer to check whether a particular target has maneuvered in the recent past, possibly while the observer was away from the display on other bridge duties. However past position, if used can clutter the screen and should be avoided in heavy traffic as the plots of different targets start crossing and overlapping each other and should be used with caution.

13. MARK: The MARK menu enables the officer to mark any prominent target or a point of particular interest. For example, you can use the trackball to select the desired mark from the mark box at the left side of the screen. Also, you can drop anchor mark by entering the Anchor coordinates provided by VTS in port areas in the Mark menu. Right-click to open the mark menu and use L/L to enter the coordinates.

14. TARGET TRACKING/ AIS DATA BOX: appears on the right side of the radar screen. It provides information of automatically or manually acquired targets including display of range, bearing, course, speed, CPA and TCPA, BCR and BCT. The target list provides a comprehensive data display of all targets being tracked. To acquire a target on the radar screen, simply move the cursor to the target and left click. The TARGET ACQUIRE key on the keyboard can also be used to acquire the target. The CPA limit box can be used to set the range and time for CPA as required. If a target is predicted to breach the CPA limits, the alarm will sound and/or displayed.

15. PRESENTATION MODES: Radar users must clearly understand what they are seeing. North up relative motion is the normal default radar display format. Within that relative and true vector and trails can be selected. The North Up mode shows the targets in their true (compass) directions from own ship, North being maintained up on the screen. The heading marker changes its direction according to the ship’s heading. If the TRUE motion is used, own ship and other moving targets move according to their course and speed. Fixed targets such as landmasses appear as stationary echoes. In the pictures above, the presentation mode used is North Up Relative Motion.

The radar display provides the operator a bird’s eye view where other targets are portrayed relative to own ship. It is an invaluable aid to navigation. Proper use and close monitoring of the radar especially in reduced and restricted visibility can help avoid the close quarter situation and/or collision. It is therefore important that all radar users understand its use and have a thorough knowledge of the equipment.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

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Introduction to GMDSS

During the 18th century, the ships sailing in international and coastal waters were dependent on the Morse code to send any kind of distress signal to a coastal authority or ships in the nearby vicinity during an emergency.

Since it was a transmission of texture information using tones or lights, this kind of message was never very clear to understand what kind of emergency onboard ships.

Therefore, an internationally agreed safety procedure was adopted by IMO under SOLAS chapter IV which is known as GMDSS- Global Maritime Distress Safety System.

GMDSS and its Uses

On 1st Feb 1999, the fully implemented GMDSS came to picture. It was a set standard for usage of communication protocol, procedures and safety equipment to be used at the time of distress situation by the ship.

Under GMDSS, all the passenger ships and cargo ships above 300 GT involved in the voyages in international waters have to carry equipment as per GMDSS.

Read -> SOLAS requirements for GMDSS 

When a ship uses GMDSS, it basically sends a distress signal via a satellite or radio communication equipment. It’s also used as a medium for sending or receiving maritime safety information and general communication channel.

Read -> Daily, Monthly and Weekly Tests Of GMDSS equipment on board Ships

In the GMDSS framework, there are different Sea Areas to allot the working equipment in the respective area. They are as follows:

To understand the above table further, the following are the ranges with regard to the frequencies in a specific band:

1. Medium Frequencies: 300 KHz to 3 MHz
2. High Frequencies: 3 MHz to 30 MHz
3. Very High Frequencies: 30 MHz to 300 MHz

Very High Frequencies (VHF)

For the purposes of maritime communication, the range of 156 MHz to 174 MHz is allocated. Channel 16, which is set at 156.800 MHz, is for Distress, Urgency and Safety communication. Channel 70, set at 156.525 MHz, if for routine VHF DSC (Digital Selective Calling) watch.

GUARD channels are set put above and below Channel 16 to avoid any interference on Channel 16. One cannot have seamless traffic on Channel 16 with interference with regard to other communication aside from distress, safety and urgency. So the Guard channel frequencies are 156.775 MHz and 156.825 MHz.

Among other things, the VHF set runs on a 24 Volt DC supply with J3E type of transmission for Radiotelephony and G2B type of transmission for VHF DSC.

The different elements of GMDSS are as follows:

1.  INMARSAT:  It is a Satellite operated system that includes ship earth station terminals – Inmarsat B, C and F77. It provides telex, telephone and data transfer services between ship-to-ship, ship to shore, and shore to ship along with a priority telex and telephone service connected to shore rescue centres.
2.  NAVTEX: NAVTEX is an internationally adopted automated system which is used to distribute MSI-maritime safety information, and includes weather forecasts and warnings, navigational warnings, search and rescue notices and other similar safety information.
3. Emergency Position Indicating Radio Beacon (EPIRB): EPIRB is equipment to help determine the position of survivors during a SAR operation. It is a secondary means of distress alerting. Read about EPIRB here.
4.  Search and Rescue Locating Equipment: Primarily the Search and Rescue Radar Transponder. This is used to home Search and Rescue units to the position of distress which transmits upon interrogation. Read about Search and Rescue equipment here.
5.  Digital Selective Calling (DSC): This is a calling service between ship to ship, ship to shore or vice versa for safety and distress information mainly on high or medium frequency and VHF maritime radio.

Documents to be carried onboard with regard to GMDSS:

1. Ship’s Radio License
2. Radio Operators Certificates
3. Safety Radio Certificate
4. GMDSS Radio Log Book
5. ITU List of Cell Signs and Numerical Identities of Stations used by Maritime Mobile and Maritime Mobile Satellite Services
6. ITU List of Coast Stations
7. ITU List of Ship Stations
8. ITU List of Radio determination and Special Service Stations
9. Antenna Rigging Plan
10. Valid Shore Based Maintenance Certificate

GMDSS Training

The handling of GMDSS equipment requires certified training as well as licensing from the Telecommunication department of the department. The General Operators Certificate (GOC) is mandatory in order for an officer to be allowed to handle GMDSS equipment onboard the ship.

To obtain this GOC, a short course is compulsory to attend following which an exam is conducted (written and oral), which needs to be cleared.  This training is aimed at Cadets who ought to become licensed Radio Operators to operate all the equipment in conjunction with the regulations laid out for GMDSS.

The training period is around 12 days and owing to the course being mandatory, it is advised to call into an approved institute to book a seat for a future date, well in advance. Depending on which country the individual is from, they must check the respective institute websites as well as the Ministry of Shipping (or whichever applicable for their country) website to get the full details on eligibility and criteria for admission into the GMDSS course.

Over the period of the course, the officer is taught about the various aspects of GMDSS ranging from Radio Log to sending INMARSAT messages and all such aspects of it which will be required when carrying out communication onboard. The written exam tests the theory whereas the oral examination is a one on one session with a surveyor who tests the individual on the different aspects of GMDSS, covering the whole syllabus (theory as well as practical).

Recommended GMDSS Books:

GMDSS – A Guide For Global Maritime Distress Safety System

GMDSS – A User’s Handbook

Admiralty List of Radio Signals (ALRS) Volume 5: GMDSS

NP285 or ALRS Vol. 5 is the publication with extensive information in theory as well as practical use for all things pertaining to the GMDSS. Correction for this is found in Section 6 of the weekly Notices To Mariners (TNM). Its contents cover as follows:

1. Distress Communication And False Alert
2. Operation Procedure For Use Of DSC Equipment
3. Search And Rescue Transponder
4. Extract From ITU Radio Regulations
5. VHF DSC List Of Coast Stations For Sea Area A1
6. MF DSC List Of Coast Stations For Sea Area A2
7. HF DSC List Of Coast Stations For Sea Area A3
8. INMARSAT
9. Maritime Safety Information (MSI)
10. SafetyNet
11. NAVTEX
12. Distress, Search And Rescue

Portable Marine Radio

The portable marine radio or the survival craft transceiver, a very important element of the GMDSS, is a piece of equipment located in the bridge in case the ship’s personnel have to board the survival craft but they may be used for communication on board as well.

In case it’s used in an emergency, it is used for on-scene coordination between the survival craft and the search and rescue units. The IMO requirements for the survival craft transceivers are as follows:

1. Can be operated by unskilled personnel
2. Transmission and Reception on 156.8 MHz (Channel 16) and 156.3 MHz (Channel 6)
3. Withstand a drop of 1 meter
4. Watertight to a depth of 1 meter for 5 minutes
5. Minimum power of 0.25 watts
6. A power reduction switch available
7. The antenna must be omnidirectional and vertically polarized
8. Battery power capacity for 8 hours (Nickel Cadmium or Lithium Battery)

The scope of GMDSS is vast and extensive reading on it, through publications and manuals and all other available means is the only way to get better at handling the equipment and gain further knowledge about the setup.

Being a mandatory setup onboard ships which is also the key setup with regard to emergency situations, it is actually in self-interest for the ship’s officer to gain maximum know-how on every aspect of the GMDSS.

You might also like to read:

• Daily, Monthly And Weekly Tests Of GMDSS Equipment On Board Ships
• SOLAS requirement for Global Maritime Distress Safety System (GMDSS)
• A Guide To Verified Gross Mass (VGM) For Shipping
• How to get a GMDSS Endorsement Certificate?
• What is An Emergency Position Indicating Radio Beacon (EPIRB)?
• What are SSB Radios?

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

This post may contain affiliate links, meaning we get a small commission if you decide to make a purchase through our links, at no additional cost to you. You can read our full disclaimer here.

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Introduction to Global Maritime Distress Safety System (GMDSS) – What You Must Know appeared first on Marine Insight - The Maritime Industry Guide

The development of a uniform system of buoyage throughout the world was of paramount importance for safe navigation at sea.  As traffic lights are used to guide drivers on road, similarly buoys and beacons are indispensable for guiding mariners at sea.

Imagine what would have happened if more than one buoyage system was in use around the world. Different buoyage system means different rules, in complete conflict with one another.  It would cause confusion and lead to accidents.

With the aim of improving navigational safety to act as a barrier to dangers to shipping and to solve differences of opinions, efforts were made to establish a single set of rules by IALA  – INTERNATIONAL ASSOCIATION OF MARINE AIDS TO NAVIGATION AND LIGHTHOUSE AUTHORITIES, which gave them a choice of using red to port or red to starboard, on a regional basis.

For the sake of maintaining uniformity in buoyage system worldwide, IALA divided the world into two regions – Region A and Region B.

Region A includes Europe, Australia, New Zealand, Africa, the Gulf and some Asian countries whereas Region B comprises of North, South, Central America, Japan, Korea and the Philippines.

IALA proposed a system allowing the use of lateral marks in each region, but whereas in region A, the colour red of the Lateral System is used to mark the port side of channels and the colour green for the starboard side.

In region B, the colours are reversed. Regional variations do not pertain to cardinal, isolated danger markings, safe watermarks or special marks.

IALA buoyage system provides six types of marks:

• Lateral marks
• Cardinal marks
• Isolated danger Marks
• Safe Water Marks
• Special Marks
• Emergency Wreck Marking Buoy

1. LATERAL MARKS: The lateral marks help to indicate which side of the waterway is to be followed. The port marks should be kept to the vessel’s left side and starboard marks to its right.

However, when a vessel travels downstream, the position of marks will change accordingly, i.e. port marks on its right side while starboard marks on its left.

When a channel divides to form more than one way, a modified lateral mark is then used to indicate the “preferred channel”. A preferred channel is indicated by red and green horizontal bands on the lateral mark.

If you find that the marks are numbered, it indicates that the sequence follows the conventional direction of buoyage.

Every buoy is identified by their colour, shape, top marks, light and the rhythm of light.

The table below will give a better illustration of the buoys found in Region A and B respectively.

LATERAL MARKS REGION A:

LATERAL MARKS REGION B:

2. CARDINAL MARKS : 

Cardinal marks are used in conjunction with the compass to indicate where the mariner may find the best navigable water. They take their name from the quadrant in which they are placed. They have the same colour and same shape irrespective of the regions A and B.

There are 4 cardinal marks named after the four cardinal points of the compass; NORTH, SOUTH, EAST AND WEST. Each mark can be distinguished from one another from their top marks, buoy colour and rhythm of light.  When a cardinal mark is seen, remember that clear and navigable water lies on the named side of the mark.

So suppose that you are on an easterly course and you see a north cardinal mark ahead of you, it should strike to your mind that safe navigable water is on the north side of the cardinal mark, and therefore you should alter your course to port.  Cardinal marks are also used to draw attention to a feature in a channel such as a bend, junction, branch or end of a shoal.

Remembering the buoys and its top marks is not a challenge if you commit these key points to memory- North and South cardinal top marks are pretty easy to remember as they follow the direction North and South.

North cardinal top marks point upwards while the south top marks point downwards. East cardinal top mark pretty much takes the shape of an egg and can be associated with the Easter egg. West cardinal top mark can be compared to the waist of a woman – tapering towards the centre.

The rhythm of light can be related to the face of a clock. All cardinal marks exhibit white light. The table below describes the light rhythm for each cardinal mark.

Note that Quick flashing light (Q) has a flash frequency of 50 to 60 flashes every minute and a Very Quick flashing light (VQ) has a flash frequency of at least 100 to 120 flashes every minute.

3. SAFE WATERMARKS: 

Unlike other marks that use horizontal stripes, this is the only mark to use vertical stripes. Safe watermark does not point to any danger but specifies that safe navigable water is all around the mark.

Safe water marks are instrumental to mariners as they indicate the beginning of a marked channel. So when a mariner sees a safe watermark on a chart, he should soon realize that he is approaching a channel.

It is the demarcation between open sea waters and confined waters.  It indicates the entrance to any port. It also points out the best point of the passage under a fixed bridge.

Safe watermark uses a red ball as a top mark. Safe watermarks can be used in a line to mark navigable safe water route through shallow areas.

4. ISOLATED DANGER MARKS:  

As the name suggests, these buoys are used to mark dangers to shipping. They highlight and bring to the attention of mariners any hazards or dangers to safe navigation.

These marks are erected or moored above the danger to alert mariners of any peril ahead. An isolated danger mark indicates that there is navigable water all around the mark.

These marks can be distinguished from other marks by their top marks, which consist of 2 black spheres one above the other and by their colour – black with one or more red horizontal bands. The rhythm of light, group flashing 2 can easily be retained in memory by correlating to its top mark -2 black spheres.

5. SPECIAL MARK:  

Special marks are used to denote mariners’ areas with special features. They do not play any major role in facilitating mariners in safe navigation. They only point out areas of certain interests to mariners. The nature of such areas can be found by consulting the charts or Sailing Directions.

Special marks may indicate spoil grounds, military exercise areas, recreational zones, boundaries of anchorage areas, cables and pipelines, Dead ends, mooring areas, protected areas, marine farms or aquaculture, oil wells, ODAS(Ocean Data Acquisition System) which gather information about wind speed, pressure, salinity and temperature.

These marks can easily be demarcated from other buoys by their yellow colour and topmark which is a cross.

6. EMERGENCY WRECK MARKING BUOY: 

These buoys have come into existence much later compared to the other 5 types of marks. The sinking of the MV Tricolour in the Dover Strait in 2002 introduced the emergency wreck marking buoy in the IALA buoyage system.

The wreck was struck further by 2 other ships causing havoc damage to shipping and loss of life. Post this incident, it was immediately necessary to mark such new dangers so that it is readily recognized by ships as a new hazard and further collisions are prevented from occurring.

Emergency wreck marking buoys mark newly discovered unsurveyed dangers which are yet to be announced and declared in nautical publications and charts.

This buoy is placed as close as possible to the wreck and unlike other buoys, is designed to provide a highly conspicuous visual and radio aid to navigation.

Had IALA not emerged with the idea of having a uniform, single buoyage system worldwide, there would have been lots of confusion and conflict among seafarers navigating all over the world and safety of navigation would be jeopardized.

IALA maritime buoyage system has helped to overcome these difficulties to a great extent s thereby aiding mariners of all nationalities, navigating anywhere in the world to fix their position and avoid dangers without fear of ambiguity, now and for the years to come.

IALA which is a non-governmental body has worked dedicatedly over the years to exchange information and recommend improvements to navigational aids based on the latest technology.

The implementation of IALA buoyage system began in the 1980s. Still many of the countries across the globe remain to adopt and follow the IALA system. The change to the new system, although gradual is happening slowly.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

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