Introduction
1.2 Radar users and uses
ships have grounded through sole reliance on very precise (but faulty) satellite navigation, ignoring the more woolly but independent radar coastline echo.
8. Make landfall. Since the advent of satellite navigation, this long-range task has lost some of its former importance.
The relationship between radar suppliers and deck-officer operators is often tenuous.
The radars may be procured by the shipowner, owner's purchasing manager, ship management company or shipbuilder, perhaps as a just-compliant product within a third party's overall bridge electronics deal rather than on technical merit. Repair and maintenance is perhaps in the hands of independent contractors, and the operators may be provided by a manning or ship management agency. One unfortunate result is that designers receive insufficient feedback on how well their products actually perform in the rough and tumble of actual service, rather than under controlled laboratory test conditions.
1.2.2 Leisure craft
Beside general navigation, the skipper or helmsman operates radar for obstruction avoidance, monitoring position of competitors when racing and sometimes to detect sea or precipitation clutter - to find smoother water, fairer weather or a good racing wind. Special radars have evolved for leisure craft.
1.2.3 Fishing vessels and small commercial vessels
The watchkeeper is usually the skipper or mate, who operates the radar for most of the above tasks. In addition fishing vessels have to detect dan buoys which mark nets, monitor activities of other fishing vessels, perhaps hope to detect flocks of birds feeding on fish and use clutter returns to help keep an eye on the weather.
The bigger yacht radars are often also fitted to small commercial vessels such as tugs and harbour workboats which are too small to have to carry radar within the international Safety of Life at Sea Convention (SOLAS, Section 1.4.5) but which choose to do so for operational convenience and safety. The International Maritime Organisation (IMO) has produced guidelines on appropriate performance for two radar sizes.
1.2.4 High speed craft
Collision avoidance is usually the first priority for fast ferries and other high speed craft (HSC). They use slightly modified conventional marine radar, augmented by night-vision infrared optical sensors for waterlogged obstructions which are poor radar targets.
1.2.5 Vessel traffic services
VTS systems provide a service to shipping, while technically similar vessel traffic management and information services (VTMIS) provide vessel movement data to
Figure 1.2 Dover Maritime Response Co-ordination and Control Centre (MRCC), UK Maritime and Coastguard Agency. On 80 m cliff commanding exten- sive views of the English Channel. Takes data from radar outstation at Hastings. Operates in conjunction with Port of London Authority and French CROSS radar networks. Reflector scanner operating in dual frequency diversity mode at 9GHz. Eight workstations, three being dedicated to emergency responses. Reproduced by permission of UK Maritime and Coastguard Agency, Norcontrol-IT and Easat
the port management. For our purposes we shall lump them together. VTS oper- ators, sometimes called watchstanders, use radar to gain awareness of the traffic situation, confirm manoeuvres and positions reported-in by radio or by the radio- based automatic identification system fitted to all ships over 300 gross tons (AIS;
from 31 December 2004) and maintain tracks on all significant targets within the surveillance area. At the shorter ranges, ships' aspect is often of considerable inter- est in confirming reported manoeuvres. Moves are afoot in IMO to introduce long range identification and tracking of ships by AIS for security purposes, which may necessitate some form of integration with VTS radar displays.
An increasing number of systems akin to VTS are being installed to monitor shipping movements within traffic separation schemes (TSS) for safety purposes.
Figure 1.2 shows one such station and Figure 1.3 shows a typical tower-mounted scanner.
At the other end of the scale, coastal surveillance radars are used by coastguard and voluntary organisations to keep a safety watch on inshore craft near popular leisure resorts, particularly where currents can so often cause problems to the inexperienced, see Figure \A(a)-(c).
1.2.6 Military applications
For general navigation, in naval parlance Marine and Pilotage (M&P), many warships carry navigational radar generally similar to those on merchant ships. The radars we shall describe are devoid of any form of anti-jamming facilities (electronic protec- tion, formerly called electronic counter-countermeasures, ECCM) and are unsuited to warfare. However, outfits similar to VTS and marine radars are used for safety surveil- lance of coastal gunnery and missile-firing ranges, and although little publicised,
Figure 1.3 High gain reflector scanner for sea surveillance service at 9GHz.
Inverse cosec2 type, aperture 5.5 m, gain 4OdBi, switchable circular and horizontal polarisation. Steel tower also carries transmitter- receivers and communications equipment, plus infrared and CCTV cameras. Reproduced by permission of Easat Antennas Ltd, Stoke on Trent, UK
increasingly for drug, intruder and piracy interdiction by coastguard or gendarmerie services. The majority use frequencies in or near the marine 9 GHz band. Equip- ments vary from powerful (^250 kW) sets with massive reflector scanners derived from military practice and displaying in a VTS-like range control centre, down to the smaller deep-sea ship sets or even yacht radars, deployed in small rough-terrain vehicles. Performance can be predicted from the following chapters, but we shall not cover the specialist precision tracking pulse or frequency-modulated (FM) radars which follow the flight of the projectile and of its sub-munitions.