Which description defines a turning point (TP) in leveling?

• A. An intermediate point between two bench marks upon which foresight and backsight readings are taken to enable a leveling operation to continue from a new instrument position.
• B. Elevation of the line of sight of an instrument.
• C. Reading taken on a rod held on a point whose elevation is to be determined.
• D. Horizontal angle observed clockwise from any reference meridian.

Answer: (A)

A turning point in leveling is an intermediate point between benchmarks used to transfer the level from one instrument position to another, allowing foresight and backsight readings to be taken so the leveling operation can continue from a new setup. This point provides a way to maintain vertical control as you move the instrument along the route, which is essential for propagating elevations accurately. The other descriptions refer to different ideas: the height of the instrument’s line of sight, a single staff reading on a point to determine its elevation, or a horizontal angle measurement, none of which define the transfer point used to continue a leveling run.