# Surveying Questions and Answers – Compass – Magnetic Declination

This set of Surveying Multiple Choice Questions & Answers (MCQs) focuses on “Compass – Magnetic Declination”.

1. The horizontal angle between the true meridian and the magnetic meridian shown by needle at the time of observation is called ______
a) True bearing
b) Magnetic bearing
c) Arbitrary bearing
d) Magnetic declination

Explanation: Magnetic declination at a place is the horizontal angle between the true meridian and the magnetic meridian shown by needle at the time of observation.

2. If the magnetic meridian is to the right side of the true meridian, declination is said to the _________
a) eastern
b) western
c) southern
d) northern

Explanation: Magnetic declination at a place is the horizontal angle between the true meridian and the magnetic meridian. If the magnetic meridian is to the right side of the true meridian, declination is said to the eastern.

3. If the magnetic meridian is to the left side of the true meridian, declination is said to the _________
a) eastern
b) western
c) southern
d) northern

Explanation: Magnetic declination at a place is the horizontal angle between the true meridian and the magnetic meridian. If the magnetic meridian is to the left side of the true meridian, declination is said to the western.

4. If the magnetic meridian is to the right side of the true meridian, declination is said to the positive.
a) True
b) False

Explanation: Magnetic declination at a place is the horizontal angle between the true meridian and the magnetic meridian. If the magnetic meridian is to the right side of the true meridian, declination is said to the eastern or positive.

5. If the magnetic meridian is to the left side of the true meridian, declination is said to the negative.
a) True
b) False

Explanation: Magnetic declination at a place is the horizontal angle between the true meridian and the magnetic meridian. If the magnetic meridian is to the left side of the true meridian, declination is said to the western or negative.
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6. What is the systematic departure of the declination from its mean value during a period of 24 hours?
a) Diurnal variation
b) Annual variation
c) Secular variation
d) Irregular variation

Explanation: The Diurnal variation or daily variation is the systematic departure of the declination from its mean value during a period of 24 hours. It generally varies with the phase of the sunspot period.

7. The variation which has a yearly period is known as _________ variation.
a) Diurnal variation
b) Annual variation
c) Secular variation
d) Irregular variation

Explanation: The variation which has a yearly period is known as annual variation. The declination has a yearly swing of about 1′ or 2′ in amplitude. It varies from place to place.

8. Which of the following variation to appear to be of the periodic character and follows a sine curve pattern?
a) Diurnal variation
b) Annual variation
c) Secular variation
d) Irregular variation

Explanation: Due to its magnitude, secular variation is the most important in the work of the surveyor. It appears to be of periodic character and follows a roller coaster pattern.

9. Which of the following variations are due to magnetic storms?
a) Diurnal variation
b) Annual variation
c) Secular variation
d) Irregular variation

Explanation: The irregular variations are due to what are known as magnetic storms, earthquakes and solar influences. They may occur at any time and cannot be predicted.

10. Find the magnetic declination at a place if the magnetic bearing of the sun at noon is 188°?
a) 8° W
b) 4° W
c) 8° E
d) 4° E

Explanation: At noon, the sun is exactly on the geographical meridian. Hence the true bearing of the sun at noon is zero or 180° depending upon whether it is to the north of the place or to the south of the place. Since the magnetic bearing of the sun is 188°, the true bearing will be 180°.Now, True bearing = magnetic bearing + declination then 180° = 188° + declination. Simplifying we get declination = 8° W.

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