2 July 2016

Radio Detection And Ranging-RADAR-Ship Navigation Systems-ETO

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RADAR  (Radio Detection And Ranging)

Marine radars are X band or S band radars to provide bearing and distance of ships and land targets in vicinity from own ship (radar scanner) for collision avoidance and navigation at sea.
Radar is a vital component for safety at sea and near the shore. Captains need to be able to maneuver their ships within feet in the worst of conditions and to be able to navigate "blind". This means inside a dark room with no visibility they need to safely navigate their way through waters in the worst of weather. Radars are rarely used alone in a marine setting. In commercial ships, they are integrated into a full system of marine instruments including chartplotterssonar, two-way radio communication devices, and emergency locators (SART).
The integration of these devices is very important as it becomes quite distracting to look at several different screens. Therefore, displays can often overlay charting, radar, sonar into a single system. This gives the captain unprecedented instrumentation to maneuver the ship. With digital backbones, these devices have advanced greatly in the last years. For example, the newer ones have 3D displays that allow you to see above, below and all around the ship, including overlays of satellite imaging.In port or in harbour, shore-based vessel traffic service radar systems are used to monitor and regulate ship movements in busy waters.

Operation of the Marine Radars

The operation of the marine radars can be explained as follows:
There is an antenna on the top of the radar that continuously rotates and flashes
The flashes actually are frequency beams that are transmitted from the radar to find out whether there any objects present in the path of the ship
The frequency and the time taken by the flashes to return (reflections) to the radar receiver of the ship helps to find out whether the route of the boat can be continued with or not
On the display screen, the reflections can be seen so that identifying the actual distance of the objects can be even more easy
The most important point about marine radars is that the screens used to view the position of the objects are either LED screens or monochrome screens. With such perfect screens, the clarity of the objects is highlighted even further. Also since these screens are water-proof there is no threat of interruption to the ship radar system in times of rough weather.
The tracking ship system has further been developed to include even boats. This means that even boat owners can be assured of their vessel’s safety while on the water.
One major advantage of the marine radars is that the power and electricity consumption by them is far too less. This means that the marine radars are not just user-friendly but also help the ship owner to regulate the cost of power and electricity.
Radar has been a major instrument to help marine navigation since the past six decades. Over the years, the radar technology has developed to include not just aircrafts but ships as well. Marine travel and safety, thus has become very feasible. It can be hoped, that in the future more such tracking devices will be developed so that more number of marine accidents and casualties can be prevented.
S band is lower frequency than X band. It therefore has a larger antenna and is normally only found on larger vessels.
X band has better resolution and can see smaller targets due to its higher frequency, but is also more susceptible to clutter from weather than S band. Large vessels usually carry both to give them the best visibility under differing conditions.

Radar and associated equipment required by Regulation 19 of SOLAS V comprise:
  • Radar unit – 9 GHz ("X" Band)
  • Radar unit – 3 GHz ("S" Band)
  • Electronic Plotting Aid (EPA) 
    EPA equipment enables electronic plotting of at least 10 targets, but without automatic tracking.

    NOTE – The wording of the Regulation in the case of EPA includes “..or other means to plot electronically the range and bearing of targets to determine collision risk.” Therefore manual plotting equipment is no longer acceptable except for existing vessels still complying with SOLAS V/74.
  • Automatic Tracking Aid (ATA)
    ATA equipment enables manual acquisition and automatic tracking and display of at least 10 targets.
  • Automatic Radar Plotting Aid (ARPA)
    ARPA equipment provides for manual or automatic acquisition of targets and the automatic tracking and display of all relevant target information for at least 20 targets for anti-collision decision making. It also enables trial manoeuvres to be executed.
CARRIAGE REQUIREMENTS

9 GHz ("X" Band) Radar - is required on any vessel of 300 gt. and over. "X" Band radars can locate radar transponders including search and rescue transponders (SARTS).

3 GHz ("S" Band) Radar - to- be fitted as the second radar, which is required on ships of 3000 gt. and over unless the Administration considers it appropriate to carry a second 9 GHz Radar. The two radars must be functionally independent of each other. The MCA will require a reasoned case for why a 3 GHz radar cannot be carried. "S" Band radars will not detect SARTS or other radar transponders.

EPA - To be incorporated in Radar equipment on ships of 300 gt. and over, but less than 500 gt 

ATA - To be incorporated in Radar equipment on ships of 500 gt. and over (replacing the requirement for an EPA)
On ships of 3000 gt. and over the second radar must also be equipped with an ATA. The two ATAs must be functionally independent of each other.

ARPA - To be incorporated in one radar equipment on ships of 10000 gt. and over. The second unit must incorporate ATA if not ARPA.

                                     

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