Skip to main content

Compass Truism

Karl Westman of Ocean City, New Jersey, asks:"Is it all right to use magnetic headings on my chartplotter to adjust a new compass?"Tim Bartlett replies:In theory, definitely not. But in practice I'd have to give you a very guarded "maybe." The problem, of course, is that your heading is the direction your boat is pointing in. Your

Karl Westman of Ocean City, New Jersey, asks:

"Is it all right to use magnetic headings on my chartplotter to adjust a new compass?"

Tim Bartlett replies:

In theory, definitely not. But in practice I'd have to give you a very guarded "maybe." The problem, of course, is that your heading is the direction your boat is pointing in. Your chartplotter/GPS unit cannot know this. It only knows the direction the boat is moving, known as your "track" or "course over ground."

And there can be a big difference. For example, if you are doing 6 knots with a 3-knot current on your beam, there's a difference of almost 30 degrees between your heading and your track. Buf if you should be lucky enough to have a perfectly calm day and there is no tide or current to affect the boat's course over the ground, the track shown by your chartplotter should be the same as your compass heading if the compass is adjusted properly.

A good way to check your compass is to aim your boat at a fixed landmark or buoy, and then take the magnetic bearing of the landmark by placing your chartplotter's cursor on it. Then compare that bearing with the compass heading. As long as the landmark is more than a mile or so away, the bearing shown by the chartplotter should be the same as the compass heading, give or take a degree.

Related

IOD-spins-and-others

Corinthian Classics

The 24th running of the Corinthian Classic Regatta, held August 13 and 14, is a testament to the beauty of traditional and modern classic racing yachts and offers a chance to look back at the yachting legacy in Marblehead and also look forward to the future. This year’s regatta ...read more

20220815

VIDEO: Small but Mighty

This summer has been a great one for sailors everywhere, but in particular for the 87 sailors participating in the Tiwal Cup on France's Gulf of Morbihan. In addition to some great sailing, the event saw a new record on the books--fastest ever assembly of the inflatable dinghy. ...read more

00-LEAD-210918_11HR_AZIMUT48HRS_AMO_00411

11th Hour Racing Team's Green Mission

“I’ll admit, it’s still hard to watch the boat leave the dock sometimes,” says former Volvo Ocean Race sailor Mark Towill. Since meeting during a Transpac campaign over 15 years ago, he and his teammate Charlie Enright have sailed thousands of miles together aboard two Volvo ...read more

D61_JKELAGOPIAN-3

Boat Review: Dufour 61

Dufour, long one of France’s most well-respected builders, has been producing sailboats in La Rochelle since the dawn of fiberglass boatbuilding. Having recently merged with another La Rochelle-based builder, Fountaine Pajot, Dufour has now joined other European mass-production ...read more

m138123_14_00_210609_TORE02_SE_2152_2504-2048x

The Ocean Race to be “Climate Positive”

The 2023 Ocean Race intends to be one of the world’s first climate positive sporting events, offsetting more greenhouse gasses than are produced. The two-fold effort means cutting emissions by 75 percent and investing in ocean projects that sequester carbon and restore ocean ...read more

01-LEAD-Ancients-3-2048x

Cruising Lake Superior

Almost anywhere a sailor drops the hook someone else has been there before. We are hardly ever the first. That remote Maine harbor without a soul in sight: there’s a lobster trap. The south coast of Newfoundland: the crumbling remains of a fisherman’s cabin lie hidden among the ...read more

01-LEAD-Tablet-Holder-4

Fabricating a Tablet Holder

During the pandemic, I was stuck aboard Guiding Light, a Lagoon 410, in St. Lucia for over a month. During that time, as I worked on the boat, I started by doing a spring cleaning in my spares locker and finding some parts and material that I forgot I had. As soon as I saw them, ...read more

00-LEAD-AdobeStock_486335954

A Catamaran for a New Era

Anacortes, Washington, is an unassuming sea-salty town near the San Juan Islands of Puget Sound, and the Betts Boats yard is easy for a passerby to miss. But within Betts’ facilities, the dawn of an era in Pacific Northwest production boatbuilding could be breaking with the ...read more