Answer: C. Elevations along a straight line
Profile levelling is usually done for determining elevations along a straight line.
Levelling is the process to determine the relative position of points on the earth's surface. The different types of levelling are given below.
Profile levelling: The profile levelling is usually done for determining elevation of points at a known interval along a straight line is measured.
Cross-sectional levelling: In cross-sectional levelling, the elevation of points on each side of mainline is determined
Precise levelling: Precise levelling is used to establish the major control points which need to be measured with a high degree of precision. Example precise levelling is used to determine the elevation of Benchmark.
Reciprocal levelling: In reciprocal levelling, the elevation of a point is measured with two reciprocal levelling positions such as reciprocal levelling is used to measure elevation difference of both sides of a river.
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