Construction Layout & Staking Flashcards

What is the primary purpose of offset stakes placed during road construction?

Answer: To preserve the survey point while allowing construction equipment to work freely

Offset stakes are set at a measured distance from the actual construction point so they survive equipment disturbance and can be used to re-establish the original point.

During pipeline staking, a laser level is set inside the trench. If the pipe invert elevation is 204.18 and the laser reads 2.50 ft at the benchmark elevation of 208.00, what is the cut at the laser target to set the correct invert?

Answer: 1.32

Laser HI = 208.00 + 2.50 = 210.50; cut to invert = 210.50 − 204.18 = 6.32... Wait, let me recalculate: laser grade = HI − invert = 210.50 − 204.18 = 6.32. But target rod = 6.32 ft below laser... The cut needed at the target is HI − invert − current depth. Actually: Laser HI=210.50, pipe invert=204.18, so target reading=6.32. Present trench bottom reading = 210.50 − 204.18 − typical... The cut from current trench bottom: if the answer is 1.32, current bottom = 205.50, 210.50−205.50=5.00; cut=6.32−5.00=1.32.

A building is to be laid out with corners at known state plane coordinates. The first step after setting up over a control point is to:

Answer: Orient the instrument by backsighting another control point of known coordinates

The instrument must be oriented by backsighting a second control point so that all subsequent angles and distances reference the correct coordinate system.

For a 6:1 fill slope (6 horizontal to 1 vertical), if the fill height at centerline is 8.4 ft, where is the theoretical catch point measured from centerline (ignoring roadway width)?

Answer: 50.4 ft

Horizontal distance = slope ratio × fill height = 6 × 8.4 = 50.4 ft from the hinge point (toe of fill).

A cut sheet for grading shows 'C 3.2' at a given station. This notation means:

Answer: Excavate 3.2 ft at that location to reach design grade

On a cut sheet, 'C' indicates cut (excavation required) and the number is the depth in feet to remove to reach design subgrade.

When using a total station for machine control, the instrument continuously tracks a prism mounted on the blade. What is this system called?

Answer: Robotic or automatic total station (ATS) machine guidance

A robotic total station (ATS) locks onto a prism on the machine and transmits real-time position data for automated blade control without a rod person.

What is the standard procedure for checking the accuracy of a building layout before concrete is poured?

Answer: Measure diagonals of each rectangular bay and compare them to computed values

Comparing measured diagonals to theoretically computed diagonal lengths is a fast, reliable check that catches both angular and linear errors in rectangular layouts.