Certified Photogrammetrist Photogrammetric Data Acquisition

Question 1

A frame camera has a 5 µm pixel size and a 100 mm focal length. Flying 2,000 m above terrain, what is the approximate ground sample distance (GSD)?

Accepted Answer

10 cm

Answer

GSD = pixel size × H / f = 0.000005 m × 2000 m / 0.1 m = 0.10 m.

Question 2

To obtain a photo scale of 1:12,000 with a 152.4 mm focal length camera, what flying height above average terrain is required?

Accepted Answer

1,829 m

Answer

H = f × scale denominator = 0.1524 m × 12,000 = 1,828.8 m.

Question 3

Each photo covers 2,000 m on the ground in the flight direction and the plan calls for 60% endlap. What is the air base between exposures?

Accepted Answer

800 m

Answer

Air base = (1 − 0.60) × 2,000 m = 800 m.

Question 4

An aircraft flies at 60 m/s with a shutter speed of 1/500 s and no forward motion compensation. How far does the ground move during exposure?

Accepted Answer

0.12 m

Answer

Ground motion = 60 m/s × 0.002 s = 0.12 m.

Question 5

Why do flight planners typically raise endlap to 80% or more for urban true-orthophoto projects?

Accepted Answer

To minimize occluded areas caused by tall buildings

Answer

Higher overlap provides multiple views of each point so building lean and occlusions can be resolved.

Certified Photogrammetrist Practice Test