Surveying Principles and Practices Flashcards

In a closed traverse, the angular closure error is distributed by the Compass Rule. What does this rule assume?

Answer: Errors are proportional to the length of each course

The Compass Rule (Bowditch Rule) distributes closure error in proportion to each course's length relative to the total traverse length.

What is the purpose of a backsight when using an automatic level?

Answer: To establish a known elevation on the rod and compute the Height of Instrument

A backsight is taken on a benchmark or turning point of known elevation to compute the Height of Instrument (HI = elevation + rod reading).

Which map projection preserves true directions from a central point, making it useful for navigation charts?

Answer: Gnomonic

The Gnomonic projection is the only projection on which all great circles appear as straight lines, making directions from the center true.

A surveyor measures a slope distance of 250.00 ft at a vertical angle of +3°30'. What is the approximate horizontal distance?

Answer: 249.31 ft

Horizontal distance = slope distance × cos(vertical angle) = 250.00 × cos(3°30') ≈ 249.31 ft.

In the State Plane Coordinate System (SPCS), which projection is used for states or zones with a greater east-west extent?

Answer: Lambert Conformal Conic

Lambert Conformal Conic is used for zones elongated east-west, while Transverse Mercator is used for zones elongated north-south.

When referencing a property corner, what information should a witness corner contain?

Answer: Bearing, distance, and description of the true corner location

A witness corner (reference monument) must record bearing, distance, and a complete description so the true corner can be relocated.

What is 'parallax' in the context of surveying instruments, and how is it corrected?

Answer: The apparent shift of the crosshair relative to the image when the eye moves; corrected by focusing the eyepiece then the objective lens

Parallax is the apparent movement of the crosshair relative to the target when the observer's eye shifts; it is eliminated by focusing the eyepiece first, then sharpening the image with the objective focus.