Question

In photogrammetry, the 'Tilt of a photograph' refers to the angle between the

• A. lines joining the opposite fiducial marks of a photograph.
• B. normal to the plane of photograph and optical axis.
• C. vertical and the axis of the flight.
• D. vertical and optical axis of the camera.

Hint:

Tilt causes scale variation across the photograph; drift affects orientation but not tilt.

Answer 1

The Correct Option is D

Step 1: Ideal vertical photograph condition.
A photograph is considered perfectly vertical if the optical axis is exactly aligned with the true vertical direction. In this case:
- There is no tilt
- Image scale is uniform
- Relief displacement behaves symmetrically

Step 2: What is tilt?
If the camera is slightly rotated forward, backward, or sideways, the optical axis deviates from the true vertical. This angular deviation is called tilt. Tilt results from:
- Aircraft roll
- Pitch
- Camera mounting imperfections
- Vibration and turbulence

Step 3: Mathematical definition.
Let - $V$ = true vertical direction
- $O$ = optical axis of the camera
Tilt is defined as: \[ \text{Tilt} = \angle (V, O) \]

Step 4: Why other options are incorrect.
- (A) Fiducial marks relate to interior orientation
- (B) Normal to photograph plane is not used to define tilt
- (C) Axis of flight relates to drift, not tilt
Thus, only (D) matches the true definition.

Final Answer: Tilt is the angle between the vertical and the optical axis.