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Selecting a
Steering Compass
 | How they work |
A magnetic compass consists of a free-spinning
compass card that aligns itself with the earth’s magnetic field. While the
earth’s magnetic field is very strong, small magnetic fields close to the compass may
cause it to point away from magnetic north. These sources of deviation must be compensated
for by swinging the compass, and/or creating a deviation table. Swinging the compass is a
process of adjusting small compensating magnets within the compass until heading errors
are minimized.
Electronic compasses measure the relative strength of
magnetic fields passing through two coils of wire. Using sophisticated electronics, these
sensors can deduce the direction of the earth’s magnetic field. They are still
affected by local magnetic fields like steel components and speaker magnets, but they can
compensate electronically for those fields that do not change in strength or location.
One advantage of electronic compasses is that their sensors
may be mounted remotely in many cases. This allows you to place the sensor where it will
be least affected by moving magnetic fields and the motion of the boat. Of course, it does
increase the complexity of the installation.
| Mounting style
 | Compasses need to fit your boat.
There are five basic mounting styles:
The fully adjustable and reversible Bracket allows a
mounting range of over 300 degrees from overhead, through angled and vertical mounts to
horizontal surfaces. These mounting position options and your choice of mounting hardware
permits mounting from windshield or supporting frame structures, to slanted dash boards
and consoles to almost any flat, angled or vertical surface
 | Ideal for Runabouts, Center Consoles, Ski Boats, Flats
Boats, Bass Boats, Cars, Trucks, RV's and ATV's |
| 2 1/4" Direct Reading Dial with New Graphics and
Large Numerals for Easy Reading |
| Choice of Bracket, Surface or Flush Models for a
Variety of Mounting Options |
| Three Color Combinations: Black with Black Dial, White
with Black Dial or Gray with Blue Dial |
| Strong Directive Force Magnets and New Lightweight
Composite Dial for Fast Performance |
| Built-in Compensators to Correct for Deviation |
| Extra Large Diaphragm and Rugged Construction Provide
Extended Operating Temperature Range |
| High-Impact Rubber Accent Stripe |
| Built-in, 12-Volt Green NiteVu Lighting |
| 100% Repairable |
| Exclusive 3-Year Ritchie Warranty |
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| Size
A compass card is referred to by its ”apparent” size, since the dome and
fluid inside a compass magnify the actual card size. Compass-card size largely determines
the stability and visibility of the card. Simply stated, larger compasses have better
performance. This is due in part to the increased volume of the compass bowl and greater
amount of compass fluid, which damps the motion of the card. Larger compass cards can be
seen from further away and under worse light, because the numerals, markings, and lubber
lines are larger. |
| Card type
There are two basic types of traditional compasses: direct reading and flat cards.
| Direct reading cards: The heading is read from the side of the
card nearest the helmsperson. This is more logical for some users, as you don’t have
to peer into the compass to see the heading. Direct reading cards do not bisect the
compass dome, however, and therefore have more movement in rough conditions. |
| Flat cards: The heading is read by looking inside the
compass dome, on the forward side of the card. These compasses generally have lubberlines
(heading references located in the direction the boat is traveling) and additional lines
at 45° and 90° to the boat’s heading. |
| Dual reading cards: Read like both direct and flat cards. These
are almost exclusively bulkhead-mounted sailboat compasses, and can be read more easily
from the sides than conventional cards. |
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| Digital displays are how electronic compasses display a
heading. They often use cardinal and intercardinal (i.e., N, NW, W, SW, S, SE, E, NE)
descriptions as well. While we live in a ”digital world“ with digital displays
on clocks, computers, and calculators, some boaters feel more comfortable seeing the
location of a heading relative to other points of the compass. Users of electronic
navigation systems should feel right at home with a digital display, since a Loran or GPS
displays bearings to waypoints digitally. |
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