Question

Which one of the following instrument is generally used to measure the slope angle of the ground?

• A. Optical square
• B. Cross staff
• C. Abney level
• D. Cross meter

Hint:

Different surveying instruments serve different purposes. To measure the angle of slope (inclination) of the ground, a special hand instrument is used.

Answer 1

The Correct Option is C

Step 1: Understand the task.
We need the hand instrument used to measure the slope angle (inclination) of the ground.

Step 2: Check the optical square.
An optical square is used to set out right angles, not slope angles, so it is out.

Step 3: Check the cross staff.
A cross staff is also for setting out perpendicular offsets, again not for slope.

Step 4: Discard the odd option.
A cross meter is not a standard slope-measuring instrument.

Step 5: Identify the right tool.
The Abney level has a graduated arc and a bubble; by sighting and centring the bubble you read off the slope angle directly.

Step 6: State the answer.
So the instrument used to measure the slope angle is the Abney level.
\[ \boxed{\text{Abney level}} \]