Bearing: Understanding Directional Navigation in Sailing
A bearing is the direction from your vessel to another object, typically measured in degrees clockwise from true north (true bearing) or from your vessel’s heading (relative bearing). This fundamental navigation concept is essential for safe sailing, racing tactics, and maritime navigation.
Types of Bearings
True Bearing
Measured in degrees clockwise from true north (0°/360°), true bearings are the standard for navigation charts and long-distance planning. For example, a lighthouse bearing 045° true means it lies 45 degrees clockwise from true north relative to your position.
Magnetic Bearing
Similar to true bearing but measured from magnetic north. Sailors must account for magnetic variation (the difference between true and magnetic north) which changes based on global location and time.
Relative Bearing
Measured in degrees from your boat’s bow (straight ahead = 000°), relative bearings are crucial for collision avoidance and tactical sailing. Common relative bearings include:
- Dead Ahead: 000°
- On the Beam: 090° (starboard) or 270° (port)
- Dead Astern: 180°
Historical Context
Before modern navigation equipment, sailors relied on celestial navigation and magnetic compasses to determine bearings. The development of accurate bearing measurement was crucial for:
- Safe ocean navigation
- Military naval operations
- Maritime trade routes
- Coastal navigation
Practical Applications
Collision Avoidance
- A constant bearing with decreasing range indicates potential collision risk
- Regular bearing checks help determine if other vessels pose a threat
- The “constant bearing, decreasing range” rule is fundamental to maritime safety
Racing Applications
- Taking bearings to marks helps optimize tactical decisions
- Wind shifts can be measured using relative bearings
- Competitor positions can be tracked using bearings
Navigation Safety
- Position Fixing
- Cross bearings for position fixing
- Running fixes using single objects
- Danger bearings for avoiding hazards
- Anchoring
- Taking transit bearings to ensure anchor isn’t dragging
- Establishing safe swing circles
Equipment Used for Bearing Taking
- Traditional Tools
- Hand bearing compass
- Ship’s compass
- Pelorus
- Transit lines
- Modern Equipment
- GPS plotters
- Radar
- Electronic bearing lines (EBL)
- AIS systems
Frequently Asked Questions
How do you take a bearing?
- Point your compass at the target
- Read the degree measurement
- Apply any necessary corrections for magnetic variation
- Record the time and bearing
What’s the difference between relative and true bearings?
Relative bearings are measured from your boat’s heading, while true bearings are measured from true north, regardless of your vessel’s direction.
How do you convert between true and relative bearings?
- To convert true to relative: Subtract your vessel’s heading from the true bearing
- To convert relative to true: Add your vessel’s heading to the relative bearing
Best Practices for Taking Bearings
- Regular Checks
- Take regular bearings of nearby vessels
- Monitor bearing changes over time
- Record significant bearings in the log
- Safety Considerations
- Always verify bearings with multiple methods
- Use bearing checks to confirm GPS positions
- Establish danger bearings before entering tricky areas
Common Bearing-Related Terms
- Bearing Drift: Change in bearing over time
- Transit: Two objects in line creating a bearing line
- Cross Bearing: Using two or more bearings for position fixing
- Danger Bearing: A bearing indicating the edge of a hazardous area
Digital Age Applications
Modern sailing has integrated traditional bearing concepts with digital technology:
- Electronic bearing lines on radar
- GPS-based bearing information
- AIS target bearing data
- Digital compasses with bearing memory
Tips for Racing Sailors
- Mark Roundings
- Take bearings to windward marks
- Monitor competitor bearings for tactical advantages
- Use bearing changes to optimize laylines
- Strategic Planning
- Track wind shifts using bearings
- Plan mark approaches using bearing information
- Monitor fleet positions with relative bearings
Understanding and properly using bearings is fundamental to safe and effective sailing. Whether racing or cruising, accurate bearing taking and interpretation remain essential skills for every sailor.
[Contact UK Sailmakers for expert advice on racing tactics and sail trim to optimize your performance on any bearing]