Certified Photogrammetrist Surveying Principles & Spatial Analysis 4

Question 1

In differential leveling, a benchmark has an elevation of 100.00 ft, the backsight on it is 4.25 ft, and the foresight on a new point is 2.10 ft. What is the elevation of the new point?

Accepted Answer

102.15 ft

Answer

HI = 100.00 + 4.25 = 104.25 ft, and elevation = 104.25 - 2.10 = 102.15 ft.

Question 2

Why do surveyors keep backsight and foresight distances approximately equal in differential leveling?

Accepted Answer

To eliminate collimation error and curvature and refraction effects

Answer

Equal sight lengths cause collimation, curvature and refraction errors to cancel between the two readings.

Question 3

What is the approximate combined curvature and refraction correction for a horizontal sight of 1 km?

Accepted Answer

0.067 m

Answer

The combined correction is about 0.0675 K^2 m, giving roughly 0.067 m at 1 km.

Question 4

What enables Real-Time Kinematic (RTK) GNSS to achieve centimeter-level positioning?

Accepted Answer

Carrier-phase measurements with corrections from a nearby base station

Answer

RTK resolves carrier-phase integer ambiguities using real-time corrections from a reference receiver.

Question 5

A GNSS observation session reports a PDOP of 1.8. What does this indicate?

Accepted Answer

Strong satellite geometry favorable for positioning

Answer

Low PDOP values indicate well-distributed satellites and stronger position solutions.

Certified Photogrammetrist Practice Test

Certified Photogrammetrist Practice Test

Certified Photogrammetrist Surveying Principles & Spatial Analysis 4