Maritime radar standards chart new course as Internet technology goes to sea

By Jeanne Erdmann

This article originally appeared in the July 2007 issue of IEC e-tech.

"There was a mood in the market place that they wanted radar detection to improve and wanted more harmonization," explains David Hannah, Convenor of TC 80's Working Group 1.

For the past 60 years or more, marine radars have used the magnetron, which is a special microwave device that produces short radar pulses at very high frequency. Magnetrons are still in use today. Although magnetron-based marine radars are good, today's radar users demand even higher performance capabilities and these come from a surprising place: the Internet.

The recent arrival of digital microwave requirements relevant for new Internet applications, such as WiMAX, has helped make the technology affordable for maritime radar. "WiMAX is a high powered wireless Internet technology that is not restricted to a house or block of offices but can perhaps go around a small part of a town. These require higher power semiconductor devices that operate similar to radar frequencies. The advent of those devices means you can use them in radar," explains Andy Norris, Chairman of TC 80.

Much better radar performance comes from combining WiMAX technology with clever technology called pulse compression. "It means we can see small targets in very rough seas and heavy rainfall, which has always been difficult to do," says Norris.

Pulse compression allows maritime radar users to employ the smaller amplitude signals from semiconductor transmitters and preserve the Doppler information in the reflected signal, which is lost in affordable magnetron-based systems. It is the Doppler information (frequency shifts in the returned signal) that can help to distinguish between targets and clutter. This boost in sensitivity allows military performance in commercial marine radar.

"The military is using pulse compression radar systems costing millions of dollars but the marine manufacturers are bringing this price down to tens of thousands of dollars, the current price of conventional marine radars. If you're going to use a new technology it can't cost more," explains Norris.

IEC 62388, set to become available in the last quarter of 2007 provides the maritime world for the first time with an International Standard for non-magnetron based new technology in radar.

When the IMO changed the performance standard for radar, TC 80 then produced a publication that reflects the provisions of IMO in technical detail rather than as a performance standard. "This makes us different than most other IEC groups as we have to follow IMO requirements. To assist this, TC 80 members attend many IMO meetings as observers," comments Norris.

The new standard had to interface correctly with Automatic Identification Systems (AIS) and had to accommodate new radars that can display charts. "All of these changes needed to be in and that's exactly what we've done. You still get an option of radar without charts, just maps, but we felt the market will move more and more towards adding onto the radar the capabilities of displaying some layers of charts at least," says Hannah.

In many areas of the world, big ships and very small craft such as sampans come in close proximity, often in bad weather and high rainfall. In sea state 5, for instance, small trees would begin to sway in a wind that ranges from 30-39 kilometres per hour, or 17 to 21 knots.

At sea it's a different story. The water is very choppy with lots of white foaming crests. Sailors call this sea state a fresh breeze and conventional radars have difficulty detecting small craft or stationary objects in these conditions. The new standard, when combined with other systems, such as AIS boots safety in many ways:

• In coastal navigation and harbour approaches, by giving a clear indication of land and other fixed hazards;
• As a means of providing an enhanced traffic image and improved situation awareness;
• In a ship-to-ship mode for aiding collision avoidance of both detected and reported hazards;
• In the detection of small floating and fixed hazards, for collision avoidance and the safety of own ship; and
• In the detection of floating and fixed aids to navigation.

Examples of vessels covered by IMO's new radar guidelines cover everything from super tankers to cruise lines to the Queen Mary, which is any vessel from 500 gross tonnes upwards, explains Norris. Pulse compression radar gives big ships a much better chance of missing those craft because they will now appear on radar, much like a jet airliner being able to avoid small aircraft.

Unlike airliner radar, marine radar needs to detect surface hazards up to 360 degrees. The first new radar technology coming on the market is SharpEye™ made by Kelvin Hughes Ltd, headquartered in the United Kingdom. SharpEye™ is a low, power-pulse compression and Doppler radar that uses solid-state technology, which improves performance and reliability because there are no major components to wear out, explains Hannah.

"There's a very large market for these. There are literally hundreds of thousands. The new standard is not retrospective. Only ships built after July 1 need to conform. The IEC and the IMO wanted to make sure that the new standards didn't prevent new technology being used, especially since the new technology was becoming affordable for maritime use. The old standard was written for pulse radar and would have prevented new technology from being used.

Right now, testing of the new radar standard involves a combination of analyses with a pass-fail assessment. In addition radar suppliers will also submit their own recordings of radar used at sea under many weather conditions. A target simulator system would better allow comparisons between radars", explains Norris, "but the technology is not sufficiently advanced to be affordable".

Source: International Electrotechnical Commission (IEC).