The magnetic bearing of a line is
- Athe horizontal angle between any two lines
- Bthe vertical angle of a line from the horizontal plane
- Cthe horizontal angle between the magnetic meridian and the lineCorrect
- Dthe vertical angle between the magnetic meridian and the line
Solution
Concept
Magnetic bearing is the horizontal angle measured between the magnetic meridian (magnetic north line) and the survey line.
Step-by-step solution
1. Understand the term meridian: A reference line in surveying. 2. Magnetic meridian is the line pointing toward the magnetic north pole indicated by a freely suspended magnetic needle. 3. The bearing of a line is the horizontal angle made by the line with a reference meridian. 4. Therefore, the magnetic bearing is the horizontal angle between the magnetic meridian and the line. Answer: (C) the horizontal angle between the magnetic meridian and the line
Explanation
Bearing is always measured as a horizontal angle from a reference direction. When the magnetic north-south line (magnetic meridian) is taken as the reference direction, the angle is called the magnetic bearing.
Why the other options are wrong
A: This describes an included angle or angle between two lines, not a bearing. B: Vertical angle from the horizontal plane is the angle of elevation or depression, not a bearing. D: Bearings are horizontal angles, not vertical angles.
Shortcut
Bearing = Horizontal angle. Magnetic Bearing = Horizontal angle from Magnetic Meridian.
Common mistake
Confusing horizontal angle with vertical angle. Bearings are always horizontal angles.
Correct answer: C) the horizontal angle between the magnetic meridian and the line