Photogrammetric parallax — contributors to measured parallax on a photograph The stereoscopic parallax of a point measured on overlapping aerial photographs is influenced by which factors?

Civil Engineering Advanced Surveying Difficulty: Easy
Choose an option
  • A
    Ground elevation of the point
  • B
    Flying height above datum/ground
  • C
    Length of the air base (or photo base)
  • D
    Camera focal length
  • E
    All of the above

Answer

Correct Answer: All of the above

Explanation

Introduction / Context:Parallax is the apparent displacement of image points between two overlapping photos and is central to height determination in photogrammetry.

Given Data / Assumptions:

  • A standard vertical aerial photography setup with overlap.
  • Rigid camera geometry with known focal length.

Concept / Approach:

Parallax p is commonly related by p ≈ (B f)/(H − h), where B is air base, f is focal length, H is flying height above datum, and h is ground elevation. Thus, each listed factor directly influences measured parallax values.

Step-by-Step Solution:

Increase h (higher ground) → denominator decreases → parallax increases.Increase H → denominator increases → parallax decreases.Increase B or f → numerator increases → parallax increases.

Verification / Alternative check:

Analytical stereotriangulation models and mapping camera geometry yield the same dependencies.

Why Other Options Are Wrong:

  • Each single factor is indeed influential; the comprehensive option is therefore correct.

Common Pitfalls:

  • Confusing photo base (on image) with air base (in space); both relate via scale.

Final Answer:

All of the above.

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