FUNDAMENTAL SURVEYING Angles, Bearings & Azimuths 2 — Questions and Answers
Question 1: What instrument is used to directly measure horizontal and vertical angles in modern surveying?
- Dumpy level
- Total station or theodolite (Correct answer)
- Planimeter
- Alidade
Correct answer: Total station or theodolite
A total station (or theodolite) measures both horizontal and vertical angles electronically, and most also measure distances with a built-in EDM.
Question 2: Measuring a horizontal angle in both the direct and reverse positions of a theodolite (face left and face right) is done to:
- Double the precision of distance measurement
- Eliminate instrumental errors such as eccentricity and collimation error (Correct answer)
- Determine magnetic declination automatically
- Compute elevation differences from angle data
Correct answer: Eliminate instrumental errors such as eccentricity and collimation error
Face-left and face-right measurements cancel out systematic instrumental errors including horizontal collimation error, vertical axis error, and circle eccentricity.
Question 3: A vertical angle of -5 degrees 30 minutes indicates the line of sight is:
- Directed upward from the instrument
- Directed downward (a depression angle) (Correct answer)
- Horizontal
- Below the geoid
Correct answer: Directed downward (a depression angle)
Negative vertical angles (depression angles) indicate the target is below the instrument's horizontal plane.
Question 4: What is 'grid north' in the context of US state plane coordinates?
- The direction toward the geographic North Pole
- The north direction of the state plane coordinate grid lines (Correct answer)
- The direction a compass points in a given state
- The azimuth corrected for magnetic declination only
Correct answer: The north direction of the state plane coordinate grid lines
Grid north is the direction of the northing (y-axis) grid lines in a state plane coordinate system, which differs slightly from true north except along the central meridian.
Question 5: Converting a bearing of S 45 W to an azimuth gives:
- 135 degrees
- 225 degrees (Correct answer)
- 315 degrees
- 45 degrees
Correct answer: 225 degrees
S 45 W means 45 degrees west of south; azimuth = 180 + 45 = 225 degrees.
Question 6: What is the 'angle to the right' (clockwise angle) measurement method?
- Measuring deflection angles only to the right of the backsight
- Measuring all horizontal angles clockwise from the backsight to the foresight (Correct answer)
- Measuring angles from the previous course counterclockwise
- Measuring interior angles from north
Correct answer: Measuring all horizontal angles clockwise from the backsight to the foresight
Angles to the right are measured clockwise from the backsight direction to the foresight direction, the standard convention used in most US traverse surveys.
FUNDAMENTAL SURVEYING Angles, Bearings & Azimuths 2
What instrument is used to directly measure horizontal and vertical angles in modern surveying?