In Photogrammetry, the relief displacement of a point on a vertical photograph is
- AInversely proportional to the flying height above the datum.
- BDirectly proportional to the distance of the image point from the principal point.
- CZero for a point located exactly at the nadir point of the photograph.
- DAll of the above are correctCorrect
Solution
Concept
Relief Displacement in Photogrammetry
Formula
d = (r × h) / H
Explanation
1. Write down the formula for relief displacement: d = (r \* h) / H, where d is relief displacement, r is radial distance from principal point, h is object height, and H is flying height above datum. 2. Analyze the formula relationships: relief displacement (d) decreases with flying height (H), increases with radial distance (r), and equals zero at the nadir point where r = 0. 3. Evaluate the options and select Option (d) since statements A, B, and C are all correct.
Shortcut
To remember relief displacement relationships, use the formula d = (r × h) / H: - Direct with distance (r) & height (h): Further from center or taller object = Greater displacement - Inverse with flying height (H): Higher flying altitude = Smaller displacement - Zero at Nadir: At the exact center (r = 0), displacement is zero
Common mistake
A common mistake is selecting Option A or Option B after recognizing a single correct mathematical relationship in the formula d = (r · h) / H, without reading through all the options to realize that Option D ("All of the above are correct") is the overall correct choice. Another frequent error is confusing relief displacement (which acts radially from the nadir/principal point) with tilt displacement (which acts radially from the isocenter).
Correct answer: D) All of the above are correct