Field Procedures & Data Collection Flashcards

What is the primary purpose of performing a two-peg test on a level?

Answer: To determine the collimation (line-of-sight) error of the instrument

The two-peg test compares readings from two setups to reveal whether the line of sight is truly horizontal.

A steel tape standardized at 68°F is used at 88°F to measure 100.00 ft. Using a coefficient of 0.00000645/°F, what is the temperature correction?

Answer: +0.013 ft

Ct = 0.00000645 × (88 − 68) × 100 = +0.013 ft, positive because the tape expanded.

A crew member records a wrong number in the field book. What is the accepted way to correct it?

Answer: Draw a single line through it and write the correct value nearby

Field notes are legal records, so original entries must stay legible and never be erased.

Why do surveyors try to keep backsight and foresight distances about equal in differential leveling?

Answer: To cancel collimation error and curvature/refraction effects

Equal sight lengths make systematic errors equal on both sights, so they cancel in the elevation difference.

A backsight of 4.52 ft is taken on a benchmark with elevation 100.00 ft, then a foresight of 3.17 ft on a turning point. What is the elevation of the turning point?

Answer: 101.35 ft

HI = 100.00 + 4.52 = 104.52; elevation = 104.52 − 3.17 = 101.35 ft.

What device helps a rod person hold a leveling rod plumb during readings?

Answer: Rod level (bull's-eye)

A circular rod level attached to the rod shows when the rod is vertical.

When taping down a steep slope, what technique keeps measurements horizontal?

Answer: Breaking tape into shorter horizontal segments and plumbing down at each end

Breaking tape lets the crew hold short horizontal sections and transfer points with a plumb bob.