Vertical aerial photography — effects and properties on a true vertical Which statements about a truly vertical aerial photograph and relief displacement are correct?

Introduction / Context:
Vertical aerial photographs are central to photogrammetry and mapping. Understanding principal, plumb, and isocentres and the nature of relief displacement is essential for accurate plotting and height interpretation.

Given Data / Assumptions:

• Truly vertical exposure (tilt ≈ 0).
• Positive relief features (hills) and lower areas (valleys).
• Central projection geometry.

Concept / Approach:

On a true vertical, the optical axis is vertical; hence the principal point equals the plumb point (and the isocentre). Relief displacement radiates from the principal point; higher points are displaced outward, appearing farther from the principal point and at a slightly larger image scale than lower points at the same radial direction.

Step-by-Step Solution:

Verification / Alternative check:

Relief displacement formula derives from similar triangles in central projection; mapping texts present the proportionality d = (r * h) / H for small relief relative to flying height H.

Why Other Options Are Wrong:

• Each individual statement accurately describes vertical photo geometry; thus the combined option is correct.

Common Pitfalls:

• Confusing true verticals with tilted photos where principal, plumb, and isocentre do not coincide.

Final Answer:

All of the above.