Construction Surveying
This domain tests layout and verification for construction. Expect questions on control, stationing, horizontal and vertical curves, grades, earthwork, tolerances, and as-built surveys.
Core rules
- Construction layout starts from project control and benchmarks, not from arbitrary site points. Check control before setting anything.
- Stationing is measured along a baseline; 10+00 means 1,000 ft.
- Horizontal curve: tangent T = R tan(delta/2); length L = R x delta in radians; external E = R(sec(delta/2) - 1); midordinate M = R(1 - cos(delta/2)).
- Degree of curve has arc and chord definitions; using the wrong one shifts curve geometry.
- Vertical curve: K = L/A, where A is the algebraic difference in grades in percent. Elevations follow a parabola.
- Earthwork volumes use average end area or prismoidal methods.
- As-built surveys compare constructed positions with design and document tolerances.
Worked example
A curve has R = 500.00 ft and delta = 40 degrees. T = 500 tan 20 = 181.99 ft. L = 500 x 0.698132 = 349.07 ft. If the PI is at station 10+00.00, PC = 1,000.00 - 181.99 = 8+18.01. PT = 818.01 + 349.07 = 11+67.08.
Traps
- Using the chord definition of degree of curve when the design uses arc.
- Making station arithmetic errors across the 10+00 break.
- Reversing cut and fill signs.
- Computing K with A in decimal instead of percent.
- Setting out grid distances as ground distances.