Question

An 18 in long rebar is driven into the ground until it touches an underground pipe. A backsight to a benchmark with an elevation of 393.66 ft is taken with an automatic level. The backsight has a rod reading of 7.56 ft. A foresight is taken to the rod resting on top of the rebar. The rod reading is 1.01 ft. What is the elevation of the top of the pipe

Answer 1

398.71 ft

Explanation:

Length of rebar = 18 inches = 1.5 ft

Elevation = 393.66 ft

Reading of backsight on Benchmark= 7.56 ft

Rod reading = 1.10 ft

First step : determine height of Instrument been used

= elevation + backsight on Benchmark

= 393.66 + 7.56 = 401.22 ft

Elevation of top of rebar

= 401.22 - 1.01 = 400.21 ft

Finally determine the elevation of the top of the pipe

= 400.21 - length of Bar

= 400.21 - 1.5 = 398.71 ft