Levelling applications – purpose of profile levelling along a line Profile levelling is typically carried out in order to determine which of the following for design and earthwork planning?

Introduction / Context:
Levelling serves many survey tasks: general mapping, contouring, cross sections, and detailed longitudinal profiles. A design team often needs the ground elevations along a proposed centerline for a road, canal, pipeline, or transmission line. This procedure is known as profile (or longitudinal) levelling. The question checks your understanding of its specific deliverable.

Given Data / Assumptions:

• A line (straight or laid out by chainage) is chosen on the ground.
• Staff readings are taken at regular intervals and at critical points (change of gradient, culverts, intersections).
• Reduced levels are computed for all chainages.

Concept / Approach:

Profile levelling outputs a longitudinal section—elevation versus chainage—used to design gradients, earthwork, and drainage. It is different from contouring, which gives a plan of equal-elevation lines over an area, and from property surveys, which define legal boundaries. Reservoir capacity estimation relies on area–elevation curves derived from contouring or bathymetry, not merely a single profile.

Step-by-Step Solution:

Verification / Alternative check:

Design drawings for linear projects always include a longitudinal profile and usually cross sections, confirming the purpose of profile levelling as elevations along a line.

Why Other Options Are Wrong:

Contours of an area: requires systematic area levelling or photogrammetry.

Reservoir capacity: derived from contour areas, not a single profile.

Boundaries: a cadastral task relying more on traversing than on detailed profiles.

Common Pitfalls:

Using too coarse an interval, missing breaks in slope, and neglecting cross profiles where side earthworks matter.

Final Answer:

Elevations along a straight (or selected) line