Marine Navigation Compasses

A compass is the most crucial navigational instrument used on board a marine vessel.

Learning how to use a compass to navigate is easy

Whether you are on a sailboat or a motorboat, a fixed reference is an essential aid to pointing the vessel in the planned direction. If you do not have a distinguishable reference on the horizon (or stars), then the compass is your only option.

How To Use A Compass & GPS

Developments in modern technology, such as Global Positioning Satellites (GPS), aid us with navigation when boating. However, unlike a compass, no other tool or instrument will tell you the exact direction your vessel is pointed. GPS will show you the direction you are headed, whereas the compass will tell you the direction you are pointing.

So why’s that important? Because where you are heading and where you are pointed are not the same thing! Current causes a sailboat to move over the ground in a direction different from that in which the boat is pointing. Even if there is no current, a yacht also carries leeway (sideways drift to leeward) which pushes the boat off course. Together, the leeway and current will cause a boat’s track to be very different from its heading. If the skipper is unaware of this fact, he could be in for a big navigational shock!

Calculating A Course To Steer Using A Compass

What makes the compass a unique tool is it’s ability to tell you exactly which direction you are steering in. It has definitely not been made redundant by electronic devices, like GPS, but works to enhance their navigational purpose.

For example, if you compare the COG (course over ground) from the GPS to the course you steer by compass, you can detect if there is a cross current. By using simple calculations, you can find out the direction and speed of the current and plan your course to steer to offset it. The GPS cannot tell us the correct course to steer, but we may use it to check the accuracy of the compass.