Surveying and Geomatics Flashcards

Two cross-sections 100 ft apart have areas of 120 sq ft and 180 sq ft. Using the average end area method, what is the earthwork volume in cubic yards?

Answer: 555.6 cy

V = ((A₁ + A₂)/2) × L = 150 × 100 = 15,000 cu ft; 15,000 ÷ 27 = 555.6 cy.

A photogrammetric map has a scale of 1:20,000. A distance measured on the map is 3.5 cm. What is the actual ground distance?

Answer: 700 m

Ground distance = 3.5 cm × 20,000 = 70,000 cm = 700 m.

If D = A + B where A = 100.00 ± 0.02 ft and B = 200.00 ± 0.03 ft (independent measurements), what is the propagated error in D?

Answer: ± 0.036 ft

Error in sum = √(eA² + eB²) = √(0.02² + 0.03²) = √(0.0013) ≈ 0.036 ft.

What is the primary purpose of a control survey in an engineering project?

Answer: To establish a reference framework of accurate points for all subsequent surveys

Control surveys establish horizontal and vertical reference monuments that all project surveys are tied to, ensuring consistency across the entire project.

A traverse line runs from Point A (N 100.0, E 200.0) to Point B (N 240.0, E 350.0). What is the bearing of line AB?

Answer: N 47°00' E

Bearing = N arctan(ΔE/ΔN) E = N arctan(150/140) = N arctan(1.071) ≈ N 47°00' E.

The prismoidal formula for earthwork volumes gives more accurate results than the average end area method primarily when:

Answer: The middle cross-section area differs significantly from the average of the two end areas

The prismoidal correction is largest when the mid-section diverges from the simple average of end sections, accounting for the actual curved shape of the excavated solid.

A total station reads 42°18'30" to Point B and 89°42'15" to Point C from Point A. What is the horizontal angle from B to C measured at Point A?

Answer: 47°23'45"

Angle B-to-C = 89°42'15" − 42°18'30": borrow 60" → 75"−30"=45"; (41'−18')=23'; (89°−42°)=47°; result = 47°23'45".