Search This Blog

Tuesday, January 18, 2011

Navigation at Sea - What is a buoy ??

ALL of us who drive vehicle know the importance and meaning of Road signs meant for road safety.  There are Mandatory or Regulatory signs, Cautionary or Warning signs and Informatory Signs.   Then there are various marking such as :  Central line marking,  Centre Barrier line marking, Double white / yellow lines, Combination Of Solid And Broken Lines, Stop line,  Give Way lines and more.   With passion in marine, have also heard of Nautical charts which are meant to facilitate pilotage and navigation. 

When you travel from one place to another, especially when you are stranger to that place, you require clear guidance and specified landmarks for reaching the destination.  That means someone should have traversed in that route and should have identified some significant places to serve as indicatory landmarks.  This becomes increasingly difficult when the speed of travel is higher.   Again, you have red lines and lead boards all along the High ways, which leads and gives clear direction to the destination.  Imagine, how this will happen at sea ? 
aerial view of chennai shore and lighthouse

Have also wondered the utility value of  modern day light house, which was earlier in the High Court premises and  in the late 1970s shifted to its present position opposite to AIR.  Initially the rotating lights that flashed caused some discomfort and accidents to road users near the santhome stretch of beach road.  Understand that the minimum height is calculated according to trigonometry to yield the distance of the horizon in nautical miles.

Perhaps these were the  reasons why the early navigators always sailed closer to the coastal lines or in coastal routes to avoid becoming lost.    As days went by, Polaris (North Star) was used to determine the latitude in the northern hemisphere but finding out longitude was not easier.  Again the monsoon and clouds hampered navigation.   In early days, sailors used sextants with which they could observe celestial positions of the Sun, stars and planets.

The process of monitoring and controlling the movement of a craft and guiding it to the intended destination is navigation.   This is a Latin word which is the command "sail".  There are also views that "Navi" in Sanskrit means 'boat' and "Gathi" means 'speed'. The techniques involve locating the sailing position compared to known location or celestial patterns. 

The sea routes are more of patterns than a fixed road like route.  Nearer Coast, the Coast Guard operates aids to navigation comprising of markers, buoys, lights and bells that have explicit shapes and colors to provide navigation guidance to boaters.   As the navigational aids developed, there were sea marks  which served as a  pilotage aid identifying the approximate position of a maritime channel, disclosing the hazards and helped the larger ships enter the Port safely.  Some types of sea marks are : beacons, fixed to sea bed, buoys – floating objects that are usually anchored to a specific location on the sea or on a submerged object and a type of cairn built on submerged rocks, especially on calmer waters.
floating marker buoy

These sea marks indicate channels, dangerous rocks, shoals, mooring positions, submerged sea-wrecks and variety of other things.  Some would be visible only during day light whilst those having lights, reflectors, bells, whistles, radar reflectors would be visible during night as well. 

A well made nautical sea chart would indicate the marks as well by using symbols with colour, shape and other characteristics. For better identity and uniformity, the system of marks are defined by their shapes, colours and characteristic light of buoys by the International Association of Lighthouse Authorities.  For historical reasons, there are two regions of lateral marks in use. 

Pilotage is the use of fixed visual references on the ground or sea by means of sight or radar to guide oneself to a destination, sometimes with the help of a map or nautical chart.  These are helpful for guiding vessels and aircraft, hiking and Scuba diving.   These have common visual reference points which during the day would be natural features of hills, lakes, rivers and coastal features of cliffs, man made sea marks and others.  At night, it would man made nautical feature of light house, light vessel  and other illuminated towers and buildings.

Marker buoy is a floating device that can serve differential purposes.  There are sea marks, lifebuoy, sub marine communication  buoys, temporary markers and more.  Other than those marker buoys, there are some used for data collection.  The National Data Buoy Centre is one such agency which provides regular observations from a net work of buoys and automated stations.  These stations measure various parameters such as wind speed, direction, gust, atmospheric pressure etc.,

Even in the age of satellite navigation systems and modern ships awash with electronic gadgets, maritime buoys are still significant.  The seasoned mariner derives assistance from buoys on navigable channel or knowing the isolated hazard.  The distinctive colours, marks and shapes help navigator in correctly finding out the indication.  Sometimes, the channel buoys could be difficult to be viewed against a well-lit coastline, however, the flashes could be synchronised to flash together or in sequence which would make such distinction easier.

Life has changed for the better in many ways.  Now there is  GPS navigation device.  This has enabled efficient routing of vessels and enhanced safety at sea.   Global Positioning System (GPS) are equipments that receive signals for the purpose of determining the location on Earth.  GPS devices provide latitude and longitude information, and some may also calculate altitude.  Some advanced GPS devices may also contain more advanced features of interactive maps, suggestive directions and provide information on traffic conditions using real time data.

And when we read all these, the early day explorations and achievements of Sailors look even more difficult.  Explorers have fathomed sea and they were really brave, for they ventured in to an Ocean of which little knowledge was available – that was real valour and adventure !!

Regards – S. Sampathkumar.

1 comment:

  1. thanks for sharing of knowledge!
    this marker buoy is like a musical note in a vibrant sea!