Using radar to navigate — Part I

Radar is primarily a collision-avoidance tool, but when used carefully and correctly it also can be handy for general navigation. 

This is true particularly when there is a need to keep a specific safe distance from the coast, a point of land, an island, an aid to navigation or when trying to time and space a turn off or around any of the above.

One of the most under or never used features of modern radar units is the offset Electronic Bearing Line (EBL) and parallel indexing. Either of these, when used alone or together, will provide you with fast, simple and reliable distance-off monitoring capability in real time. It’s invaluable for keeping out of shoal water and avoiding groundings due to the usual “loss of situational awareness” that plagues tired, distracted or insufficiently trained deck watchstanders.

A good example is tug mariners that transit New York Harbor’s East River, when heading for or coming back from Long Island Sound. They know (or should know) to stay about a quarter mile or more off the rocks surrounding Stepping Stones Light. This has been a navigational standard for generations and occasionally someone finds out the hard way why that is.

An easy way to accomplish this is to move your radar’s cursor to an indicated relative position 0.25 NM abeam of you on the appropriate side (to starboard when eastbound), select an EBL, then offset it. The offset is typically accomplished with just one push of a designated button. Then adjust that EBL’s bearing so that it has the same relative bearing as your heading flasher (000°). They must be parallel. Then simply keep the Stepping Stones radar target on or outside of that offset EBL and you’re guaranteed your safe distance off. This works in any visibility, anywhere you have a reliable radar target. 

If you get some practice with the technique, it becomes second nature. Master it and one day it just might save you from a devastating mistake.

About the author

Joel Milton

Joel Milton has worked aboard fishing boats, pilot boats, Coast Guard cutters and small boats, dredge tenders, offshore crewboats and supply boats, towing vessels, a small container ship, and a wide variety of small craft including an inflatable yellow “ducky” The Piker.

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