Question

The angle between true north and magnetic north is called:

• A. Local attraction
• B. Magnetic declination
• C. Dip of needle
• D. Bearing

Hint:

True Bearing = Magnetic Bearing $\pm$ Declination.
Use (+) for Eastern Declination and (-) for Western Declination when calculating True Bearing.
Remember: "East is Least, West is Best" is a common mnemonic, but for True Bearing, East is Added and West is Subtracted.

Answer 1

The Correct Option is B

Step 1: Identify the reference directions used in surveying. 
In surveying practice, directions are measured with respect to different meridians.
True North points toward the Earth’s geographic North Pole and does not change with time.
Magnetic North is the direction shown by a magnetic compass needle and varies from place to place because of changes in the Earth’s magnetic field.

Step 2: Define the angle between the two meridians.
At any given location, the horizontal angle formed between the true meridian and the magnetic meridian is known as magnetic declination.

Magnetic declination can be classified as:

• Eastern (positive) declination: when magnetic north lies to the east of true north.
• Western (negative) declination: when magnetic north lies to the west of true north.

It is important not to confuse magnetic declination with other related terms:

• Local attraction: deviation of the compass needle caused by nearby magnetic materials.
• Dip: the vertical angle made by the magnetic needle with the horizontal plane.
• Bearing: a general term for the horizontal angle between a reference direction and a survey line.

Step 3: Final conclusion.
The horizontal angle between true north and magnetic north is called:

\[ \boxed{\text{Magnetic declination}} \]