Stereoscopic base and absolute parallax – key relationships Which of the following statements about stereoscopic base on photographs and absolute parallax differences is/are correct in aerial photogrammetry?

Introduction / Context:
Stereoscopic viewing of overlapping aerial photographs enables 3D perception and elevation measurement. Two core ideas are the stereoscopic base as expressed on the photos and the behavior of absolute parallax with height.

Given Data / Assumptions:

• Air base B is the camera station separation on the ground.
• Photograph mean scale is commonly written as 1:S (S is the scale denominator).
• Absolute parallax increases with object elevation for vertical photographs.

Concept / Approach:
The stereoscopic base on photographs (b) is the image separation of the two exposure stations; numerically, b ≈ B/S if S is the scale denominator. The absolute parallax of a point is the displacement between its images along the flight direction; the difference in absolute parallax between two points is primarily governed by their height difference (with minor scale variations).

Step-by-Step Solution:
Use mean scale 1:S → image distances equal ground distances divided by S → b = B/S.Recognize that absolute parallax p is proportional to height above datum for vertical photos → Δp ∝ Δh.Geometrically, the line connecting the principal point and the transferred principal point on overlap represents the stereoscopic base direction.Therefore, all listed statements are consistent.

Verification / Alternative check:
Height from parallax formula uses Δp and known camera geometry; practical stereo plotting confirms Δp tracks elevation differences.

Why Other Options Are Wrong:
“None of these” is invalid because each statement reflects standard photogrammetric relationships and definitions.

Common Pitfalls:
Confusing scale numerator with denominator; ensure b = B/S when the scale is written as 1:S. Also avoid mixing principal point with plumb point in tilted photos.

Final Answer:
All the above