In navigation, a bearing is an angle measured clockwise from a reference direction to the direction of an object. It is typically used to determine the relative position of one object with respect to another, and is expressed in degrees (°) or mils (m).
There are two main types of bearings:
Magnetic bearings differ from true bearings due to the variation in the Earth's magnetic field. This variation is known as magnetic declination and must be accounted for when converting between true and magnetic bearings.
Method 1: Using Trigonometry
To calculate the bearing of an object using trigonometry, you need to know the following:
Using the tangent function, you can calculate the bearing:
Bearing = arctan(opposite / adjacent)
Where:
Method 2: Using a Compass
If you have a compass, you can easily measure the magnetic bearing of an object:
City | Magnetic Declination |
---|---|
New York City | -12.2° |
Los Angeles | 12.5° |
London | -0.5° |
Paris | 2.6° |
Tokyo | 7.2° |
Conversion | Factor |
---|---|
True to Magnetic | Add declination if declination is east; subtract if declination is west |
Magnetic to True | Subtract declination if declination is east; add if declination is west |
Degrees | Mils |
---|---|
0° | 0 |
1° | 17.8 |
2° | 35.6 |
5° | 89.0 |
10° | 178.0 |
20° | 356.0 |
30° | 534.0 |
A hiker was lost in the wilderness and decided to use his compass to find his way out. Unfortunately, he didn't know how to use the compass properly and ended up walking in circles for hours.
Lesson: Always learn how to use your navigation equipment before relying on it.
Two friends were kayaking on a lake. One of them decided to impress the other by paddling to a distant island and back. Unfortunately, he miscalculated the bearing and ended up paddling in the wrong direction. Hours later, he realized his mistake and had to row back to where he started.
Lesson: Even experienced navigators can make mistakes. Double-check your calculations to avoid surprises.
A group of climbers was scaling a mountain when they encountered thick fog. Without a clear view of their surroundings, they relied on their compass to guide them. However, due to magnetic interference near the mountain, their compass readings were inaccurate. The climbers ended up getting lost and had to spend the night on the mountain.
Lesson: Be aware of potential navigation hazards and always carry a backup navigation system.
Pros of Trigonometry:
Cons of Trigonometry:
Pros of Compass:
Cons of Compass:
Q: How do I correct for magnetic declination?
A: Use the conversion factors in Table 2 or refer to online magnetic declination calculators.
Q: What is the difference between a bearing and a course?
A: A bearing is an angle, while a course is a direction of travel. A course can be calculated from a bearing by adding or subtracting drift (angle of sideward motion).
Q: How can I improve my accuracy when calculating bearings?
A: Practice regularly, use high-quality equipment, and double-check your calculations.
Q: What is the best type of compass for accurate bearing calculations?
A: A precision sighting compass with a mirror and adjustable declination correction.
Q: How often should I recalibrate my compass?
A: Calibrate your compass regularly, especially before long trips or in areas with magnetic interference.
Q: What other navigation tools can I use to supplement bearing calculations?
A: GPS devices, maps, and altimeters can provide additional navigation information.
掌握计算方位角的技能对于准确导航至关重要。通过了解不同的方法、策略和资源,您可以提升您的导航能力,下次在野外迷路时自信满满。
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