SMQT Fundamentals of Surveying 4 — Questions and Answers
Question 1: What is 'refraction' and how does it typically affect vertical angle observations?
- It bends light rays upward, making objects appear lower than they are
- It bends light rays downward through the atmosphere, making objects appear slightly higher than they are (Correct answer)
- It causes horizontal displacement of targets
- It only affects distance measurements, not angles
Correct answer: It bends light rays downward through the atmosphere, making objects appear slightly higher than they are
Atmospheric refraction bends light rays downward, so distant objects appear higher than their true positions, introducing a small positive error in vertical angle readings.
Question 2: When converting a magnetic bearing to a true bearing, which factor must be applied?
- Earth's curvature correction
- Magnetic declination (Correct answer)
- Sea level reduction factor
- Atmospheric pressure correction
Correct answer: Magnetic declination
Magnetic declination is the angular difference between magnetic north (where a compass points) and true geographic north, and must be added or subtracted to convert between the two.
Question 3: What is a 'turning point' (TP) in differential leveling?
- The point where the survey changes from leveling to traversing
- A temporary point where both a foresight and a backsight are taken to advance the level circuit (Correct answer)
- The highest point along a level route
- The instrument setup location
Correct answer: A temporary point where both a foresight and a backsight are taken to advance the level circuit
A turning point receives a foresight to determine its elevation, then a backsight is taken on it from the next instrument setup to carry the elevation forward.
Question 4: The term 'horizontal distance' in surveying refers to:
- The slope distance measured directly between two points
- The distance projected onto a horizontal plane, independent of elevation change (Correct answer)
- The distance measured along the ground surface
- The straight-line distance corrected for atmospheric refraction only
Correct answer: The distance projected onto a horizontal plane, independent of elevation change
Horizontal distance is the distance between two points as projected onto a horizontal plane, used for area calculations and plats regardless of terrain slope.
Question 5: Which coordinate system divides the US into zones where each state (or region) has its own projection to minimize distortion?
- Universal Transverse Mercator (UTM)
- State Plane Coordinate System (SPCS) (Correct answer)
- Geographic coordinate system (lat/long)
- Public Land Survey System (PLSS)
Correct answer: State Plane Coordinate System (SPCS)
The State Plane Coordinate System divides the US into zones, each using either a Lambert Conformal Conic or Transverse Mercator projection to keep distortion below 1 part in 10,000.
Question 6: What is 'scale factor' in the context of a map projection?
- The ratio of map distance to ground distance, which varies across the projection (Correct answer)
- The contour interval divided by map scale
- The magnification power of a survey telescope
- The ratio of ground elevation to mean sea level
Correct answer: The ratio of map distance to ground distance, which varies across the projection
Scale factor is the ratio of a distance on the projected grid to the corresponding distance on the ellipsoid; it is exactly 1.0 only along standard lines and varies elsewhere.
Question 7: In the Public Land Survey System (PLSS), what is the standard size of a 'section'?
- 1/4 mile × 1/4 mile (40 acres)
- 1 mile × 1 mile (640 acres) (Correct answer)
- 6 miles × 6 miles (23,040 acres)
- 1/2 mile × 1/2 mile (160 acres)
Correct answer: 1 mile × 1 mile (640 acres)
A standard PLSS section is one square mile, containing 640 acres; 36 sections make up one township.
SMQT Fundamentals of Surveying 4
What is 'refraction' and how does it typically affect vertical angle observations?