The marine radar is equipment that is perhaps used the most on the ship’s bridge by the OOW in carrying out a safe navigational watch. A mandatory aid to navigation, the radar is used in identifying, tracking (with integrated ARPA) and positioning of vessels (including one’s own vessel) among other things in order to adhere to the COLREGs so as to safely navigate a ship from one point to another. The marine radar is classified under the x-band (10 GHz) or S-band (3GHz) frequencies. The x-band, being of higher frequency is used for a sharper image and better resolution whereas the S-band is used especially when in rain or fog as well as for identification and tracking.
Tracking ship devices are compulsory as per COLREGS (International Regulations for Preventing Collisions at Sea). SOLAS Chapter 5, Regulation 19 states that “All ships of 3000 gross tonnages and upwards shall, in addition to meeting the requirements of paragraph 2.5, have a 3 GHz radar or where considered appropriate by the Administration a second 9 GHz radar, or other means to determine and display the range and bearing of other surface craft, obstructions, buoys, shorelines and navigational marks to assist in navigation and in collision avoidance, which are functionally independent of those referred to in paragraph.”
The entire SOLAS Chapter 5, Regulation 19 can be read here . Additionally, the Annex 16 dealing with specific information with regard to the marine radar onboard can be read here. With the help of ship radar, accidents can be prevented at sea with the use of the various inherent functionalities of the radar (determining the CPA and the TCPA, EBL, VRM etc). However, even while the ships are docked in the port, with the help of these radars, the coast guard, VTS and the other authorities can use them to monitor the traffic in the small radar range.
The ship radar has a screen (referred to as the Plan Position Indicator) that displays all the targets that are present within the radar range. Since all the objects are clearly visible on the screen, navigating and monitoring the position of the ship becomes really feasible, hence the term ‘aid to navigation’
Operation of the Marine Radars
The operation of the marine radars can be explained as follows:
- The parabolic radar antenna transmits and receives electromagnetic waves; as far as a target being displayed is concerned, that is basically the wave that bounced off a certain object that paints itself on the PPI (Plan Position Indicator)
- 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. The transmission and receiving of the pulse travels twice the distance in going and hitting the target and back; therefore, the target displayed on the PPI is basically halved with regard to its range
- On the PPI, the reflections can be seen so that identifying the actual distance of the objects can be even easier. The same paint on the PPI can be also be checked for determination of the bearing of the target
Uses of the Marine Radar
- To calculate range and bearing of a target and thereafter use the information to determine speed, course etc
- Integration with other shipboard equipment (such as ECDIS) to derive precise data
- Navigating own vessel and her course with regard to collision avoidance
- Fixing the ship’s position using terrestrial objects such as lighthouses, buoys etc
- Differentiating between targets in high traffic density areas
- Determination of the weather, to an extent
- Use by VTS in controlling coastal traffic
- Usage of features such as parallel indexing to ensure safe navigation
- Alleviating workload on the OOW on the bridge
- Used extensively in pilotage that covers the above aspects
The marine radar is a much bigger subject than is laid out in the article which only skims the surface of the operation and the uses of the radar. As an OOW, it is important to be thorough with the radar and study its operation and features extensively along with the limitations of the radar. A good book to start with is Shipborne Radar and ARPA by Capt. H. Subramaniam.
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 waterproof 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 have 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.
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