Ireland's sailing, boating & maritime magazine

The electronic chart is precise and doesn’t require any input from the operator except for putting in the required route to follow and the GPS positioning can be relied on to give an accurate position. However, radar is different story; even the sophisticated modern radar requires considerable input and interpretation from the user to get the right level of quality information out of it. The trouble is that many modern boat users endow the radar with the same qualities of precision as the electronic chart – an error that can lead them into serious trouble. Many radar users believe that if a target doesn’t appear on the radar display, then it doesn’t exist. They assume that all potential targets around them – including all the ships, boats and buoys – will show up on the display and, with all this electronic information about targets, there’s a growing belief that there’s no need to look out of the wheelhouse windows. Indeed, there are some navigators who assume that the view outside can only be a distraction and that the primary focus should be on the electronics. This is something that is affecting both ship and yacht navigators. If you think those guys out there navigating the big ships are in full control of their navigating and acting professionally, then think again. An analysis of ship collisions has established that in approximately 30% of incidents, one of the ships had not seen the other before the collision. It’s quite likely that the same applies with yachts although statistics are hard to find. Part of the cause for this can be found with the design of wheelhouses and bridges. Very few ships and yachts have any view astern and even out at the sides the outside view can be restricted by wide windscreen pillars or other obstructions. Reflections on the windscreen can make life difficult and this can be a particular problem at night. Anyway, who wants to look outside at what might be any empty ocean when there is a much better view on the electronic screens? The electronic information is presented with a precision that makes it difficult to dispute. Twenty years ago the navigator would negotiate with the electronics to find an answer but today the presentation offers little room for negotiation. But is the navigator justified in assuming that the radar is picking up all the other vessels within range? Navigators would like to believe this is the case because it makes their job so much easier. If you start to question what the radar is showing and its accuracy, then you have to go back to the basics of navigation by looking out of the windows. For many, unfortunately, that’s not an attractive proposition. The development of radar has made enormous strides since the early radars when you had to coax information out of the display. Today, advanced processing of the incoming radar signals can sort out a lot of the unwanted radar returns such as those from sea clutter. In theory, this processing should still leave the radar returns from small craft, which may be no stronger than those from the sea clutter, but because they have different characteristics this can allow them to be distinguished. Unfortunately there is no guarantee of this and small craft can be vulnerable when they are in the vicinity of shipping and there’s no guarantee that they will show up on the radar display of the ship. Kelvin Hughes claims to have solved at least some of this problem with their Sharp Eye radar. As Barry Wade from Kelvin Hughes commented, “None of what might be termed conventional radars can offer sub-clutter visibility but our Sharp Eye does. By taking technology previously only available to the military, we can offer a greatly improved capability for detecting small targets amongst sea clutter. We can also offer a much higher level of reliability and our Sharp Eye represents a step change in radar technology. However, we cannot defeat the laws of physics and so there is no 100% guarantee that every target will be detected.” It is that inability to detect 100% of the targets out there that makes small craft vulnerable. For small craft, the best solution is to have the best quality radar available so that you can see the other ships and boats, even if they cannot see you. Raymarine has introduced a new high definition radar that offers advanced processing techniques to help differentiate between the sea clutter and small craft. Furuno has an ultra high definition radar that does much the same thing. These radars should be capable of picking out most small craft on the display except in rough sea conditions where the sea clutter returns may be stronger than those from other small craft. Japanese manufacturer Koden has used advanced processing to create moving target vectors on the display in a radar designed to come between the small craft and the big ship units. These vectors lines, which indicate the course and speed of the other vessel, can help to differentiate between small craft and waves because the waves are not moving. Navigators on ships are placing an increasing reliance on what the radar is showing. A study of the way that ferries in the English Channel carry out collision avoidance in their busy waters revealed that manoeuvring tactics and collision avoidance are based on radar information alone, which shows an apparent disregard for the Collision Regulations. A route through the main shipping lanes is planned by using the vector lines from own ship and from the other ships to find an apparent safe route through. Such a system makes a commitment to the chosen route solely on the basis of the radar information. If everything is working according to plan, then the collision risks are removed, provided that everyone sticks to the plan. The trouble is that such a plan doesn’t make any allowances for small craft that may be out there and which will only show up at short range, if at all. Yachts tend to have a more cautious attitude towards using radar for collision avoidance, perhaps because skippers have less experience in collision avoidance techniques on radar. Small craft are also much more manoeuvrable than ships and can respond much more quickly to a changing situation. Then there is a realisation that small craft radar is less capable of picking up other small craft because of sea clutter. In addition, the wide beam angle of the small radars doesn’t present the clearest of displays. Most small craft radar users are aware that their radar will not necessarily show up everything that might be in ‘view’ and so they use their radars more cautiously. For yachts, investing in the cheapest or smallest radar available is not going to solve the problem. The key to radar performance lies mainly in the size of the antenna and nothing under a four-foot antenna should be considered except for small yachts. This will give a narrow beam angle that will in turn produce a sharper display. Fast craft might want to choose a radar with a faster antenna rotation that is more likely to pick up smaller targets, whilst another good solution is Simrad’s dual display where two different radar ranges can be shown on the same display. Certainly the radar should have a dedicated display and the split screen displays that show chart, radar, and other information should be avoided. Even with the best radar in the world, there’s no guarantee that you will see everything out there and you cannot expect other vessels to see you, particularly in rough seas. So despite the wonderful presentation of a modern radar display, you may not be seeing everything that is out there and radar needs to be used with caution.