Stereo plotting — effect of shifting one projector along the X-axis In a stereoscopic plotting instrument, if one projector is moved along the X-axis (changing the separation between projectors), what happens?

Introduction / Context:
Analytical and optical-mechanical stereo plotters create a 3D model by projecting left and right images with a defined relative orientation. The spacing between projectors simulates the photographic base (air base). Understanding how controlled shifts affect base, scale, and parallaxes is key for accurate model scaling and for diagnosing orientation issues.

Given Data / Assumptions:

• X-axis is taken along flight direction (or the photo x-axis) in the plotting setup.
• We consider a pure X-translation of one projector.
• Relative orientation angles are maintained (no change in rotations).

Concept / Approach:
Shifting a projector along X changes the separation of the two projectors, i.e., the simulated air base. Model scale in the X-direction is proportional to the ratio of focal length to the effective air base-to-height geometry; therefore, changing the base alters model scale. Y-parallax is associated with misalignment perpendicular to the flight direction and is not caused by a pure X-translation. As long as the angular relative orientation (tilts/rotations) is preserved, the relative orientation condition remains satisfied; only the base and scale change.

Step-by-Step Solution:

Verification / Alternative check:
Instrument manuals and analytical geometry of stereoscopy show X-parallax changes with base, while Y-parallax is controlled by angular alignment (omega/phi/kappa adjustments).

Why Other Options Are Wrong:
Each statement (a)–(d) is correct in the stated context; hence “All of the above.”

Common Pitfalls:
Confusing X-parallax (depth parallax) with Y-parallax; thinking any change in projector spacing upsets relative orientation (it does not if rotations remain fixed).

Final Answer:
All of the above