Quality Inspection Flashcards

What instrument condition does the two-peg test verify on an automatic or tilting level?

Answer: The line of sight is parallel to the level axis (horizontal)

The two-peg test detects collimation error, where the line of sight is inclined relative to the true horizontal.

In a two-peg test, why is the first setup placed exactly midway between the two pegs?

Answer: Equal sight distances cancel collimation error, giving the true elevation difference

With balanced sights, any line-of-sight tilt produces identical errors on both rods that cancel when differenced.

How is an optical plummet in a tribrach typically checked for adjustment?

Answer: By rotating the tribrach or plummet about the vertical axis and checking that the crosshair stays on the ground mark

If the plummet is out of adjustment, the projected point traces a circle as it is rotated rather than staying on the mark.

A total station is set with a -30 mm prism constant while a 0 mm prism is used. What type of error results?

Answer: A constant error of 30 mm in every measured distance

Prism constant mismatches add the same fixed offset to each slope distance regardless of length.

Which field procedure removes vertical index error and horizontal collimation error from total station angle measurements?

Answer: Measuring in both face left and face right and averaging

Direct and reverse (face I and II) observations have equal and opposite instrument errors that cancel when averaged.

Where can a survey crew verify the accuracy of its EDM against published distances in the United States?

Answer: An NGS Calibration Base Line (CBL)

NGS maintains calibration baselines with precisely known distances for checking EDM instruments.

If a leveling rod is not held plumb, how are the rod readings affected?

Answer: They are always too large

A tilted rod intercepts the horizontal line of sight higher up, so the reading is always greater than the true value.