Surveying

Benchmark

A permanent, marked point of known elevation from which a leveling run starts or closes.

A benchmark is a stable monument — a brass disk set in concrete or rock, for example — whose elevation above a datum has been established. Differential leveling begins on a benchmark with a backsight, and a well-run survey closes on the same or another benchmark to check its own error.

Temporary benchmarks are set on a project for convenience and tied to permanent ones. The difference between the closing elevation computed and the benchmark’s known elevation is the misclosure, which is distributed back through the run.

How much of the FE Civil exam is Surveying?