Radar can be a captain’s best friend, serving as electronic eyes to help safely navigate when visibility is limited. Yet there’s more to radar than watching for blips on a screen. Built-in features can help you in ways you may not have considered. Use these tips to boost safety at night or in fog or both.
Silent Sentries
Two very practical radar controls are the EBL (electronic bearing line) and VRM (variable range marker). Set your EBL on any target of interest. This will indicate the target’s direction relative to your boat. Set your VRM marker on that same object and you will see just how far away it is.
Tip: Position your ELB on any vessel that appears to be headed toward your location. Should that target continue to maintain a course down along that ELB, you’ll know that it is headed for a collision with your boat. In navigation, this is known as a CBDR (constant bearing decreasing range) scenario. Change course, speed or both to avoid a collision. If the target veers off your ELB, you will be assured that contact with that vessel will be avoided.
MARPA Magic
MARPA (mini automatic radar plotting aid) or ARPA gives you the same navigation ability as big-ship commercial radars. You can track several nearby targets and determine their speed, bearing and the CPA (closest point of approach) to your boat, as well as the TCPA (time to closest point of approach) on the screen of a MARPA-enabled radar.
Tip: Linking AIS (Automatic Identification System) reception to your radar can add additional vision. AIS-broadcasting vessels send their positions and other navigation data via VHF, which can be displayed on your radar screen, letting you “see” their position even though they are behind an island, ship, point of land or other obstacle that obscures them from radar’s line of sight.
