Differential leveling in surveying: Is differential leveling the process of using a level instrument and telescope (plus staff/rod readings) to determine differences in elevation between points?

Introduction / Context:
Differential leveling is a core technique in surveying to establish elevations of points relative to a datum. It underpins engineering design for grading, drainage, road profiles, and construction staking.

Given Data / Assumptions:

• A level instrument (optical/digital) and a leveling rod are available.
• A benchmark with known elevation relative to a vertical datum is accessible.
• Line of sight is established between instrument and rod positions.

Concept / Approach:
The method obtains a backsight (BS) reading on a known point to establish a height of instrument (HI), then takes foresight (FS) readings on unknown points. Differences in elevation are computed as BS − FS, chaining through multiple setups if needed. Results reference a common datum for consistency.

Step-by-Step Solution:

Verification / Alternative check:
Perform a level loop returning to the original benchmark. The closure error should be within allowable limits; apply adjustments if necessary. This independent check confirms the accuracy of differential leveling.

Why Other Options Are Wrong:

• Bearings only (option B) describes horizontal angle measurement, not leveling.
• GPS post-processing (option C) is a different technique (GNSS leveling).
• Shading contours (option D) is a drafting/visualization task.
• Legal descriptions (option E) pertain to deeds and plats, not elevation measurement.

Common Pitfalls:
Misreading the rod; poor instrument leveling; ignoring curvature/refraction over long sights; failing to close and check error budgets.

Final Answer:
Correct: it uses a level and telescope to find elevation differences