How to pick a compass
Get the right compass for your boat
The magnetic compass, an essential navigation tool, has stood the test of time and still provides the best means to help you steer, especially when your electronic navigation fails. Make sure you know what makes a good compass and how to select the right one for your boat.
Select the best compass you can reasonably afford and fit on the boat. Larger is generally better. The top-reading style, with a flat or slightly concave card, has several benefits over front-reading models.
A quality compass should have repeatable readings. To check this, turn the compass in different directions and back to the original heading to see if it reads the same way each time. Without moving the compass, you can also draw the compass heading away using a metallic object. See if it returns to the original reading once you remove the object. Avoid any compass that does not return to the same reading for a given heading.
Dampening softens a compass’s response to turns and motion on a boat. Dampening should average out the bumps but not alter the compass’s final reading. Powerboat and sailboat compasses are dampened differently; make sure to select a compass with the correct dampening for your boat type.
Ease of use
A good compass should be easy to read and interpret. Small front-reading compasses have compressed scales with fewer graduations. Shown backward, the directional scale on a front-reading compass can lead to confusion in steering; for example, W (west) is shown to the left of S (south) on the scale, but if you turn the boat left, you will be heading east.
Larger top-reading compasses have more detailed scales. With its scale graduated in the familiar direction, a top-reading compass is more intuitive, and the compass bowl magnifies the compass card, making it easier to read.
To learn more about using your compass to navigate, take a Piloting course at a squadron near you.
Good compasses have solid construction with no visible bubble above the fluid in the bowl. They will also have built-in compensation magnets to adjust for errors.