FUNDAMENTAL SURVEYING Coordinate Geometry (COGO) & Area Calculation 2 — Questions and Answers
Question 1: What is the 'elevation factor' in state plane coordinate computation?
- The ratio of Earth's radius to (Earth's radius + elevation) (Correct answer)
- The number of feet gained per mile of horizontal distance
- The vertical scale on a topographic map
- The correction for atmospheric refraction at a given elevation
Correct answer: The ratio of Earth's radius to (Earth's radius + elevation)
The elevation (sea-level) factor = R divided by (R + h), where R is Earth's mean radius and h is the average elevation, reducing ground distances to sea-level distances.
Question 2: Point A is at coordinates (1000, 2000) and Point B is at (1300, 2400). What is the distance AB?
- 500 ft (Correct answer)
- 700 ft
- 300 ft
- 400 ft
Correct answer: 500 ft
Distance = sqrt((1300-1000)^2 + (2400-2000)^2) = sqrt(90000+160000) = sqrt(250000) = 500 ft.
Question 3: In COGO, the 'inverse' calculation determines:
- A new point location from a known point using bearing and distance
- The bearing and distance between two known coordinate points (Correct answer)
- The interior angles of a traverse from coordinate data
- The area of a parcel from GPS observations
Correct answer: The bearing and distance between two known coordinate points
Inverse computation takes two known coordinate points and calculates the bearing (or azimuth) and distance between them.
Question 4: What is a 'section' in the US Public Land Survey System (PLSS)?
- A 640-acre square parcel that is 1 mile by 1 mile (Correct answer)
- A quarter-mile square parcel of 40 acres
- A 36-square-mile township
- A 160-acre parcel (one quarter section)
Correct answer: A 640-acre square parcel that is 1 mile by 1 mile
A section is a nominally 1 mile by 1 mile square of land containing 640 acres, and 36 sections make up one township.
Question 5: The 'forward problem' (radiation) in COGO computes:
- The bearing and distance between two points
- A new point's coordinates from a known point using bearing and distance (Correct answer)
- The area enclosed by a series of coordinates
- The closure error of a traverse
Correct answer: A new point's coordinates from a known point using bearing and distance
The forward (or direct) problem calculates the coordinates of an unknown point using a starting point, bearing, and distance.
Question 6: One township in the PLSS contains how many sections?
- 6
- 16
- 36 (Correct answer)
- 64
Correct answer: 36
A township is a 6-mile by 6-mile square divided into 36 sections, each nominally 1 mile by 1 mile.
FUNDAMENTAL SURVEYING Coordinate Geometry (COGO) & Area Calculation 2
What is the 'elevation factor' in state plane coordinate computation?