FEATURE - New Radar
Despite the rapid advancement in marine navigation technology, radar is the only real-time information system available to boaters, reports bright spark KEVIN GREEN
It lets us see in the dark, watch out for other boats, allows us to chart a course in fog and remains a quick way of finding the range of an object. I’m talking about radar and its history is interesting. Claims to its invention are numerous, but my favourite anecdote is from the WWII when its use was pioneered by the British Royal Air Force, allowing the vastly under-resourced RAF to send up squadrons to intercept incoming enemy aircraft.
Avoiding danger is a major reason for fitting a radar set to a boat these days. But nowadays the technology can do much more than that, with add-on features such as Automatic Identification System (AIS) information and collision-avoidance software for layering data across the screen.
Radar sets are made up of several main components with the scanner housed in a dome, or rotating arm, which contains an antenna, transmitter and receiver. The screen transforms the electrical pulses emitted and received into an image for the user to view.
The black box in radars, the magnetron, generates this pulse, which is fired out via the rotating antenna that typically runs at 24 or 48rpm. Range is measured by recording the time between the pulse transmitted and the echo received back.
One of the main drivers for recent development was tighter regulation, around 2003, of the frequencies used -9.3 to 9.4gGhz (known as X-band) — which prompted manufacturers to be more rigorous and resulted in increased processing power of the scanner-transmitter technology.
This has been dubbed as ‘digital’ technology by manufacturers, but in reality is an enhancement of an existing process. However, this has also led to improvements in displaying the data, and to all the major brands — Furuno, Garmin, Lowrance, Northstar, Raymarine and Simrad — to have digital radars.
Leading brand Navico took this process one major step further by replacing the magnetron with a Frequency Modulated Continuous Wave (FMCW) transmitter to further enhance the quality of the emission frequency and dubbed their technology as ‘broadband’.
For the sailor, the benefits are several, including clearer displays and a choice of add-on technologies to layer over the top, such as MARPA collision-avoidance. But there are several choices to be made when looking at radar.
To begin with, do you want a simple standalone set? These are not so common nowadays because radars are becoming part of integrated navigation systems. However, Furuno has a popular entry-level set in this area: the Furuno 1623.
More likely, the radar will integrate with a chartplotter or PC and, via NMEA protocols, be able to combine GPS and electronic charting at once. These multifunction displays (MFD) such as Garmin’s latest 5000 touchscreen range come with high-definition graphics and are compliant to the latest NMEA 2000 standards, allowing them to be interfaced with other manufacturers’ kit.
BIGGER THE BETTER
Size indeed matters when it comes to radars, so the bigger the scanner the more information you receive. Traditionally on small yachts scanners are enclosed in domes, called radomes, and for motorboats and larger vessels the naked (and more powerful) rotating arm scanners are used.
The popular analogy used is of a light beam — the more powerful the torch, the more that can be seen. Scanners are rated from around 2.2kW (the Furnuno 1623) to more than 25kW. The size of their beam (both horizontal and vertical) typically is a few degrees, with the aforementioned Furuno being 6.2° wide.
In the vertical plane, beams are typically angled at around 10° to 30°, or more to compensate for the motion of the boat. Of course, the narrower the beam the more precise the area scanned, so a narrow beam might differentiate two vessels close together, whereas a wider beam won’t.
BEST RADAR FOR YOU
When considering radar, think about your own boating. If you regularly go offshore you may want to have a greater range to your radar and be able to distinguish other boats so a more powerful unit of 4kW or above with a narrow beam would be ideal. Alternatively, if you work in confined waters a less powerful and wider-beam model would do, giving you more closer-in information.
Just be aware that most technology has limitations. For instance, radars are line-of-sight in operation, much like VHF radio, so the higher the scanner is situated, the farther its range.
To paraphrase the RYA Navigation Handbook (2003), to calculate the radar’s horizon use the equation 2.2 xvH, where H is the height of the scanner in metres and the answer is in nautical miles. So if your scanner is 4m above the water, its horizon is about 4.5nm away. If it's 9m high, its horizon is 6.5nm away. That may not sound very much, but remember that a big ship may well be over 25m high, which means its superstructure will be visible when it is 10nm beyond the horizon.
Reading a radar screen is not generally an intuitive process so, like any other piece of complex equipment, it is wise to have at least a one-day course on the use of it.
When you switch on the screen it will typically show a dotted line running from the centre, your location, to the top of the screen. This is generally called the Electronic Bearing Line (EBL) and can be rotated to an object, which will give you a bearing of that object. In this head-up radar display that bearing is given relative to the boat’s heading. The other important screen feature is the Variable Range Marker (VRM), which is adjusted to cover a target on the screen and then give a distance figure.
Ideally, operate the system in enclosed waters where you can check the radar image with the outside scenery. Familiarise yourself with the screen profile of your home port so that in the event of fog, or a night-time approach you will be less apprehensive. Note that high-definition displays will give you more detail so could be worth the extra cash. Learn how to adjust the clutter to compensate for rain and wave motion. More advanced users may be able to identify rogue waves at night and avoid weather systems approaching.
Competition is strong in the radar market and in recent years some of the fundamental technology has varied, which further differentiates players in the sector. For instance, companies such as Navico promote the lower emissions of its FMCW (broadband) transmitters, compared with magnetrons, as being a safety feature.
The screen output from this technology is excellent for close-range imaging, such as tricky approaches to harbours or picking out fishing buoys in the fog. Furuno counters this theory with their dual power/range mode, which allows the operator to use one radar on two different range scales. A skipper can divide his or her Furuno NavNet 3D display into two radar screens. One side operating on a low range, say 0.5nm and the other operating totally independently on a higher range scale, say 6nm.
Dominant player in the sailing market, Raymarine, offers its Super HD Digital Radar, which claims greater ranges, an extra narrow beam giving excellent target differentiation and market leading screen clarity. On the other hand, Raymarine still offers traditional no-frills analogue radar with low-power 2kW radome and mono-colour display.
For the powerboater and anglerm the Lowrance brand will always be relevant. A strong R&D company, it has brought out its own range of broadband radar. But it also has entry-level 18in radomes and 2kW sets.
Other players in the radar market include Japanese builder Koden, who offers powerful long-range sets, and popular brand Simrad, a company now under the Navico umbrella and benefiting from the group’s overall R&D power. US-based Garmin, a strong player in screen technology and GPS, is a newer entrant in this market and offers a range of narrow beam sets with HD units and rotor-arm scanners at the top end, right down to small-yacht radomes.
Radar is a developing and it’s a rich market right now, highlighted by energy efficient scanners, fantastic screens and the amazing power of integrating multifunction devices. So, I’d say it’s never been a better time to consider radar.
Radar Key features/controls
Range - adjustable
Beam (for differentiating targets)
Gain – signal strength
Clutter – adjustable for weather state
Guard zones – signals alarm
Target plotting – collision avoidance
- includes antenna, transmitter/receiver
2. Display – can be stand alone or chartplotter
New radar technologies
MARPA – Mini Automatic Radar Plotting Aid for collision prevention
AIS – vessel tracking via VHF emissions.
Alarms – for anchor watch and collision prevention
Overlays – from chartplotters
Radar user statistics (from ARC 2009)
About 80 per cent of the 215 entrants in the ARC trans-Atlantic fleet had radar. The most prolific brand was Raymarine with 125 boats, followed by Furuno with 40 and Simrad with 8. In terms of reliability, Furuno was voted best, followed by Raymarine and Simrad.
Expert tips from Raymarine Technical Services
Use the Timed Transmit feature
to reduce power usage when drift fishing or sailing offshore. Further significant power savings
can come from dropping the display brightness when not required.
Modern colour radars such as Raymarine's HD and SHD
are extremely good at seeing through rain and sea
clutter - use Colour Gain to enhance the colour difference between clutter and real returns
Use Wakes to see another vessel's movement clearly.
Wakes are also very useful for highlighting the real targets amid sea clutter.
Use Radar-Chart Overlay to check whether a particular return is a buoy or a boat.
5. Make sure your electronic compass and speed sensors are calibrated, because MARPA and
Overlay depend on accurate sensor data
Head-up mode is favourite for full-screen radar; north-up is more common when split-screen with charts, as it's easier to relate targets; Radar-Chart overlay is perhaps better still. True Motion mode is great in busy waterways as moving targets clearly stand out from stationary ones.
7. You can check your chart position and accuracy
with Radar-Chart Overlay
8. To predict a target's track automatically and much more accurately than the eye,
set it as a MARPA target
9. If you suspect an error in your MARPA data
or chart overlay, check your compass and paddlewheel sensor
calibration - both are used in calculations
10. To watch for the floating container close in, and also the bulk carrier on the horizon, use Dual Range or overlay AIS.
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