Hand-Bearing Compasses – Nautic Way Maritime Bookshop

What is a hand-bearing compass used for in marine navigation?

A hand-bearing compass is a marine navigation instrument designed to measure the direction of an object observed from a vessel. It can be used to take bearings of a lighthouse, headland, navigation mark, prominent landmark or, in some situations, another vessel. The resulting bearings can be used with a nautical chart to check the vessel’s position and support both passage planning and navigation monitoring.

Unlike a steering compass, which is primarily used to maintain a heading, a hand-bearing compass is designed to sight a specific object. It is usually portable and fitted with a sighting system that allows the user to align the instrument with the target while reading the corresponding direction. Depending on the model, readings may be facilitated by a prism, optical sight, graduated compass card or illumination system.

Hand-bearing compasses remain useful despite the widespread availability of GPS and electronic charting. They support traditional coastal navigation and position fixing, and they can help verify information supplied by electronic equipment. On a sailing yacht or motorboat, a hand-bearing compass is a practical complement to nautical charts, a steering compass and other navigation instruments.

How does a hand-bearing compass work?

A magnetic hand-bearing compass uses the Earth’s magnetic field to provide a directional reference. The navigator sights a visible object, steadies the instrument and reads the angle shown on the graduated compass card. The result is normally a magnetic bearing, which must be interpreted correctly before being plotted on a nautical chart.

The reading method depends on the instrument’s design. Some models feature an optical system that helps align the target and read the graduation. Others use a simpler sighting arrangement. Ease of handling, compass-card stability and dial readability are important factors in obtaining a useful observation.

The compass should be used away from sources of magnetic interference. Loudspeakers, magnets, electronic devices, metal structures and electrical cables may affect the reading. A portable compass is therefore not automatically free from error: its position during the observation and the characteristics of the instrument must be taken into account.

Taking a bearing at sea: a practical method

To take a bearing, the navigator first selects a clearly identifiable object, preferably one shown on the nautical chart. The object is then sighted with the compass. Once the indication has stabilised, the angle is read. Recording the landmark, bearing and time is useful, particularly when the vessel is moving.

A typical bearing procedure involves the following steps:

• Identify a visible landmark and confirm its identity on the chart.

• Move away from objects that could interfere with the compass.

• Hold the instrument according to the manufacturer’s instructions and align the sight with the landmark.

• Read the value when the indication is sufficiently stable.

• Record the bearing, time and observed object.

• Apply the necessary corrections before plotting the line of position on the chart.

Accuracy depends on visibility, observation stability, instrument quality and correct identification of the landmark. A bearing taken quickly while a boat is rolling or pitching may be less reliable. If the result appears doubtful, repeat the observation.

Magnetic bearing, true bearing and nautical charts

Correct use of a hand-bearing compass requires an understanding of the difference between magnetic north and true north. True north refers to geographic north and is the reference used for directions plotted on a nautical chart. Magnetic north follows the local direction of the Earth’s magnetic field.

The angle between these two references is called magnetic variation or declination. A reading from a magnetic hand-bearing compass is normally a magnetic bearing. To plot it as a true bearing on a chart, the navigator must apply the appropriate variation correction. If the instrument or its surroundings introduce an additional error, that error must also be considered.

Magnetic variation should not be confused with deviation caused by the vessel’s magnetic properties or nearby equipment. Variation depends on geographical location and changes over time, while local magnetic interference can affect a hand-bearing compass during an observation.

Nautical charts from Shom, Admiralty, NGA and other hydrographic offices provide information used to plan and plot bearings. Navigators should use the chart information relevant to their cruising area and apply corrections in the correct direction.

Finding a vessel’s position using multiple bearings

One of the main uses of a hand-bearing compass is position checking through intersecting bearings. The method involves measuring the directions of several fixed, identifiable objects and plotting the corresponding lines on a chart.

For example, a yacht sailing near the coast may take bearings of a lighthouse and a prominent headland. After converting the readings to true bearings, the navigator plots the position lines through the observed objects in the reciprocal direction. Their intersection provides an estimated vessel position.

To improve the result, choose landmarks whose bearing lines cross at a sufficiently wide angle. Two nearly parallel lines provide a less precise fix in the direction in which they are close together. Three or more bearings can help check the consistency of the observations, but they do not guarantee that the vessel’s actual position lies inside the area formed by the plotted lines.

When the vessel is moving, bearings should be taken close together in time or corrected for the vessel’s movement. This technique remains a useful complement to GPS positioning and other navigation information.

Choosing the right hand-bearing compass

The choice of hand-bearing compass depends on how often it will be used, the conditions at sea and the navigator’s preferences.

• Sighting method: simple sight, optical system or prism reading, depending on the model.

• Readability: clear graduations, easy-to-read numbers and visibility in low light.

• Handling: stability, instrument shape and ease of aiming at a target.

• Illumination: useful for night observations when provided.

• Required precision: graduation quality, indication stability and ease of reading.

• Operating environment: ability to take bearings away from electrical devices, metal structures and magnets.

• Intended use: coastal navigation, cruising, navigation training or traffic observation.

For frequent coastal navigation, an optical model that is easy to read and handle may be preferable. For occasional use or training, a simpler instrument may be sufficient if its readings meet the intended requirements. Check the specifications of each model rather than assuming all hand-bearing compasses offer the same features.

Hand-bearing compasses and electronic navigation

A hand-bearing compass complements modern navigation systems. GPS provides a position calculated from satellite signals, while a hand-bearing compass measures the direction of a visible object from the vessel. These are different types of information, but they can be compared to identify inconsistencies and improve situational awareness.

During coastal navigation, a bearing taken on a lighthouse can help check whether the position displayed on a chartplotter is consistent with visible landmarks. If electronic positioning is in doubt, several correctly corrected bearings provide an independent method of checking the vessel’s position, subject to the quality of the observations and the chart data.

A hand-bearing compass can also be used to observe another vessel. Repeated readings of its direction can help assess its apparent movement. However, bearing observations alone do not establish distance or determine another vessel’s intentions. They must be combined with a proper lookout and other available information.

Care and good operating practices

A hand-bearing compass should be stored carefully and used according to the manufacturer’s instructions. Protect it from impact, excessive moisture if the model is not designed for such exposure, and magnetic sources that could affect its operation.

Before going to sea, check that the compass card or directional indication moves normally, the graduations are legible and the sighting system is in good condition. If readings appear inconsistent, move away from nearby equipment and repeat the observation. Comparing the result with a landmark of known direction may help identify a systematic error.

A hand-bearing compass is most effective when used alongside sound chart preparation, accurate landmark identification and a clear understanding of magnetic corrections. It helps maintain practical navigation skills even when electronic systems are available.

FAQ – Hand-bearing compasses

What is a hand-bearing compass used for?

It measures the direction of an object visible from a vessel, such as a lighthouse, headland or navigation mark. The bearings can be plotted on a nautical chart to help check the vessel’s position.

What is the difference between a steering compass and a hand-bearing compass?

A steering compass is primarily used to maintain a heading. A hand-bearing compass is designed to sight an object and measure its direction from the vessel.

How do you take a bearing with a portable compass?

Identify a landmark, sight it with the compass, wait for the indication to stabilise and read the graduation. Record the measurement and apply the necessary corrections before plotting it on the chart.

Can a hand-bearing compass be used to find a vessel’s position?

Yes. Several bearings of fixed landmarks, correctly corrected and plotted on a chart, can provide an estimated position. Accuracy depends on the angles between the position lines and the quality of the observations.

What is the difference between a magnetic bearing and a true bearing?

A magnetic bearing is measured relative to magnetic north. A true bearing is measured relative to geographic north. Magnetic variation is used to convert between them.

Can onboard equipment interfere with a hand-bearing compass?

Yes. Magnets, loudspeakers, some electrical devices and metal structures may affect the reading. Take bearings away from these potential sources of interference.

Which hand-bearing compass is suitable for coastal navigation?

A model that is easy to sight and read, with clear graduations and a stable indication, is generally suitable for coastal navigation. The choice also depends on how often it will be used and the observation conditions.

Is a hand-bearing compass useful when a boat has GPS?

Yes. It can help verify position information by taking bearings of landmarks and provides a complementary checking method independent of the GPS display.

Can a hand-bearing compass be used at night?

That depends on the model. Some instruments include illumination or an optical system suitable for low-light readings. Check the instrument’s specifications.

How can bearing accuracy be improved?

Choose a clearly identifiable landmark, hold the compass correctly, stay away from magnetic interference, repeat doubtful readings and apply the appropriate corrections before plotting the bearing on the chart.