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

The question is about identifying the term used to describe the angle between true north and magnetic north. This is a fundamental concept in the field of surveying and mapping.

Explanation:

• True North: This refers to the direction along the Earth's surface towards the geographic North Pole.
• Magnetic North: This direction points along the Earth's surface towards the magnetic North Pole, which is constantly shifting due to changes in the Earth's magnetic field.

Magnetic Declination: The angle between true north and magnetic north at a specific location is known as magnetic declination. It is measured in degrees east or west of true north. When the magnetic north is east of true north, the declination is positive, and when it is west, the declination is negative.

Correct Answer: Magnetic declination

Elimination of Other Options:

• Local Attraction: This refers to the deflection of the magnetic needle from its normal position due to local disturbances such as nearby metallic objects or electrical equipment. It is not the angle between true north and magnetic north.
• Dip of Needle: This is related to the angle made by the magnetic needle with the horizontal in a vertical plane. It is not related to the difference between true and magnetic north.
• Bearing: Bearing is the horizontal angle measured from a reference direction, typically north. It does not specifically describe the angle between true north and magnetic north.

Answer 2

Step 1: Understanding the Concept:
In surveying, there are different meridians used as reference lines.
The "True North" represents the direction towards the geographic North Pole, which remains constant.
The "Magnetic North" is the direction indicated by a freely suspended magnetic needle, which varies due to the Earth's shifting magnetic field.
Step 2: Detailed Explanation:
The horizontal angle between the true meridian (true north) and the magnetic meridian (magnetic north) at a particular location is defined as Magnetic Declination.
1. If the magnetic north is to the east of true north, the declination is termed as "Positive" or "Eastern Declination".
2. If the magnetic north is to the west of true north, the declination is termed as "Negative" or "Western Declination".
- Local attraction refers to the disturbance of the magnetic needle by nearby magnetic objects.
- Dip of the needle is the vertical angle the needle makes with the horizontal plane.
- Bearing is a general term for the horizontal angle between any reference meridian and a line.
Step 3: Final Answer:
The angle between true north and magnetic north is specifically called magnetic declination.