Using a Hand Bearing Compass for Coastal Navigation
Navigating along coastal waters in a small boat is both rewarding and challenging. While modern electronic methods like GPS provide great convenience, traditional manual methods, such as using a hand bearing compass, remain invaluable for enhancing seamanship skills, accuracy, and safety. A hand bearing compass is a wonderfully simple, practical, and reliable tool for determining your position and direction by taking bearings of landmarks. In this essay, we'll examine exactly how a hand bearing compass works, how it is used, its advantages and disadvantages, comparisons with a marine sextant, and practical advice for successful use.
What is a Hand Bearing Compass?
A hand bearing compass is a compact, portable compass specifically designed to quickly measure magnetic bearings of objects from your current position. Unlike a fixed navigation compass, a hand bearing compass is handheld and allows you to sight directly through or over the compass at distant landmarks, buoys, channel markers, or navigation aids. The measurement you take is called a "bearing," the angle measured clockwise from magnetic north to the object. These bearings can then be plotted directly onto a nautical chart to determine your boat's exact position.
How to Use a Hand Bearing Compass:
Taking bearings with a hand bearing compass is straightforward. Follow this simple step-by-step method:
1. Select Landmarks
Choose two or preferably three clearly visible landmarks identifiable both visually and on your nautical chart. Navigation aids like buoys, lighthouses, radio towers, distinctive hills, and coastal buildings are excellent landmarks to use.
2. Measure Bearings
Hold your hand bearing compass level at eye height, look through or over it, and carefully align the sight or compass needle with the landmark. Record the magnetic bearing carefully. Repeat this step for each landmark.
3. Plot Bearings on Your Nautical Chart
On your chart, use a protractor or navigation plotting tool to plot each bearing line from the landmark toward your vessel’s approximate position. Where these lines intersect is your navigational fix—your exact location. Usually, with three bearings, the plotted lines form a small triangle called a "cocked hat," and your boat will be within or very near this triangle.
Similarities Between a Hand Bearing Compass and a Sextant:
Both hand bearing compasses and sextants serve similar fundamental purposes—they allow you to determine your vessel's position accurately without relying on electronic navigation devices. Both instruments depend essentially on angles between your boat and known fixed landmarks. Both are handheld, portable, and easy to use in coastal conditions.
Coastal navigation with either a sextant or hand bearing compass uses the same general plotting methods on a nautical chart. Each provides valuable redundancy and independence from electronic systems.
Differences Between Hand Bearing Compasses and Sextants:
However, important differences exist between the two instruments:
1. How Angles are Measured:
- Hand Bearing Compass: It measures magnetic bearings between true magnetic north and an observed landmark.
- Sextant: It measures horizontal angles directly between two visible landmarks or vertical angles of objects above the horizon. It does not rely on magnetic headings.
2. Dependence on Magnetic Variation and Deviation:
- Hand Bearing Compass: Because it references magnetic north, your bearings must be corrected for magnetic variation (difference between magnetic north and true north) and your compass deviation (errors due to your vessel’s magnetic fields).
- Sextant: Angles measured horizontally between landmarks are independent of magnetic influences. No magnetic corrections needed.
3. Accuracy and Precision:
- Hand Bearing Compass: Quick and easy but relies on careful sighting and steady hand. Errors of a few degrees may occur due to magnetic interference or sighting misalignment.
- Sextant: Potentially very precise if used carefully, often more accurate for detailed coastal navigation since angles are direct and independent of magnetism.
4. Conditions Required:
- Hand Bearing Compass: Can be used in poor visibility conditions, as long as landmarks can be identified. Does not require a clearly visible horizon line.
- Sextant: Usually requires clear visibility, identifiable landmarks, and often a clear horizon to achieve good accuracy, especially if using vertical angles.
Advantages of Using a Hand Bearing Compass:
1. Simple and Fast:
Quick and easy to use, requiring minimal practice. Excellent for beginners and small boat sailors.
2. No Electronics Required:
Reliable backup device that doesn't rely on GPS signals or batteries.
3. Works Well in All Weather:
Usable even in cloudy, hazy, or rough conditions as long as landmarks are clearly visible.
4. Affordable and Robust:
Compact, affordable, waterproof, and rugged—ideal for small boats like your Drascombe Lugger.
5. Increased Situational Awareness:
Encourages careful observation of surroundings, enhancing seamanship skills.
Disadvantages of Using a Hand Bearing Compass:
1. Magnetic Interference:
Affected by magnetic influences on board (engines, electronics, ferrous metals) requiring careful avoidance or compensation.
2. Variation and Deviation Corrections Needed:
Must correct bearings for magnetic variation and vessel deviation. Introduces additional small calculations compared to horizontal sextant angles.
3. Limited Precision:
May not be as precise as sextants in ideal conditions due to inherent compass errors and sighting inaccuracies.
Practical Uses of a Hand Bearing Compass on Small Boats:
1. Accurate Position Fixing:
Like the sextant, the hand bearing compass provides accurate coastal position fixes for confident navigation.
2. Confirming Safe Passage Through Hazards:
Taking bearings of multiple landmarks helps you navigate safely through areas of rocks, shallows, or narrow channels.
3. Quick Check of Position Underway:
Allows quick, frequent position checks while sailing along a coast. Fast and convenient compared to using a sextant.
4. Anchor Monitoring:
By taking bearings of landmarks when anchoring, later repeated bearings clearly show if your boat has dragged anchor.
Tips for Successful Use of a Hand Bearing Compass:
- Minimize Magnetic Interference: Stay clear of metallic objects or electronics when taking bearings.
- Practice Regularly: Frequent use builds accuracy, speed, and confidence.
- Select Clear Landmarks: Choose clear, distinct, and easily recognizable landmarks both visually and on your chart.
- Use Three Bearing Lines: Always try for three bearings to form a reliable and precise fix.
- Keep a Simple Compass Deviation Card: Maintain a simple deviation card onboard, noting compass errors on various headings for easy reference.
Conclusion:
For small-boat coastal navigation, a hand bearing compass is an invaluable and highly practical tool. Like a marine sextant, it offers reliable, electronics-free position fixing and navigation assistance, but it differs fundamentally in its reliance on the magnetic compass principle. Compared to a sextant, the hand bearing compass is simpler, quicker, and less weather-dependent, but it requires magnetic corrections and is somewhat less precise.
Whether a hand bearing compass or sextant is "better" depends entirely on the particular situation, your experience, and your preference. Actually, having both aboard your boat—combined with practice and familiarity—provides a superior navigation toolkit. The compass gives you quick, easy fixes in most conditions; the sextant provides precise and magnetically independent fixes when needed.
In your boat, you'll find the hand bearing compass especially valuable due to its ease, speed, simplicity, and rugged reliability. It enhances your navigational independence, boosts your seamanship skills, and provides greater safety and increased satisfaction during your coastal cruising and exploration.