Not very long ago, radar and chartplotter would have been separate, standalone items. Today's trend for multi-function displays (MFDs) has two big advantages.
Firstly, it saves cost, as only one expensive screen is needed - or more probably it enables you to have one much bigger and more versatile screen, rather than two small screens, for the same money.
Secondly it allows you to do clever tricks like overlaying the radar on the chart, or putting the two displays side by side, which was not possible before. This can be extremely helpful in interpreting the radar echoes: it shows clearly which are coming from land, which from buoys, and which from other vessels.
The chart and radar match up so convincingly that it's tempting to think that the two are intrinsically linked, but in fact they come from two completely independent sources of information. The radar display is telling you what the radar “sees” from your own yacht. The plotter display is telling you where you are according to the external GPS system.
It's often said that these days we all rely too much on GPS, and many yachtsmen would feel helpless - or at least decidedly insecure - should the chartplotter cease to function, so dependent have so many of us become. And there is always a possibility that the GPS system will fail - or be jammed, or subject to other interference.
Radar not only provides a valuable cross check for GPS, but should the GPS ever fail, it would provide an alternative source of accurate pilotage and position fixing information.
MFDs typically have an option to show waypoints on the radar display, which can be extremely useful.
The radar is also extremely good at measuring the range and bearing of a chosen object. So providing you can identify headlands, perhaps, or buoys on the display, it is easy to work up a fix using the VRM (variable range marker) and EBL (electronic bearing line) features.
In fact radar instructor Alan Watson suggests that the quickest way of obtaining a three point fix is to dispense with the bearings altogether, and merely take three ranges (distances) from three known points on the radar display, and then plot them on the paper chart using a school-type compass - one of the cheapest navigation instruments there is!
This is likely to produce an extremely close intersection of the arcs - much closer than the familiar “cocked hat” which results from the traditional three point fix taken with a hand-bearing compass. And there is no need to worry about calculating variation and deviation. Just use the VRM circle to measure the distances.
The useful range of radar installations varies according to the size of the scanner - the bigger the scanner, the longer the potential range. Typical yacht radars will have a theoretical maximum range between 24 and 72 miles.
The actual maximum radar range is actually line-of-sight, rather like VHF radio, because radio waves cannot “see” over the horizon, so the range of your radar set will also depend on how high the scanner is mounted - a scanner high on the mast will “see” further than one on a shorter pole or gantry.
The maximum range is useful for identifying land masses and weather fronts, as well large ships beyond view. But it is worth remembering that the first sight of land on the radar may not be the coastline, but could be a mountain several miles in land, which will be in the line of sight sooner than the lower land near the coast.
Shorter range scales provide greater detail of echoes close to your position. When you change the range of the radar display, you also automatically change the tuning of the scanner, to provide the most helpful information at the chosen scale.
Tip: If you have a combined radar and chartplotter, you will probably use the plotter all the time and the radar only occasionally. However, you may find that the default setting is that the radar is always on in standby mode. This wastes power. It is therefore good practice to switch the scanner off when you switch the plotter on. It means it will need a minute or two to warm up when you do want to use the radar, but your batteries will thank you!
