Which of the following statements in the context of aerial photography is/are CORRECT?
Show Hint
The camera axis and the photo (image) plane are always perpendicular to each other, so if the camera axis is normal to the ground, the photo plane must be parallel to it, not normal to it.
Oblique photographs are obtained when the camera axis is not normal to the datum plane
Tilted photographs are obtained when the camera axis is tilted from the nadir line
Vertical photographs are obtained when the camera axis is parallel to the datum plane
Vertical photographs are obtained when the photo plane is normal to the datum plane
Show Solution
The Correct Option isA, B
Solution and Explanation
Step 1: Set up the three relevant planes/lines and their standard geometric relationships. Let the datum plane be the horizontal reference (ground) plane, let the camera axis be the optical axis of the lens, and let the photo plane be the plane of the image, which is always perpendicular to the camera axis inside any standard frame camera, regardless of orientation. Step 2: Derive the correct vertical-photograph condition using this perpendicularity. For a vertical photograph the camera axis coincides with the local vertical, so it is perpendicular (normal) to the datum plane. Because the photo plane is always perpendicular to the camera axis, and the camera axis is perpendicular to the datum plane, the photo plane must be parallel to the datum plane. This shows option (D), which claims the photo plane is normal to the datum plane, is false, it should say parallel; and option (C), which claims the camera axis is parallel to the datum plane, is also false, it should say normal. Step 3: Apply the same reasoning to the oblique case. An oblique photograph is the case where this near-vertical condition is deliberately broken by a large, intentional angle, so the camera axis is measurably not perpendicular to the datum plane, which is exactly option (A), so it is true. Step 4: Apply the same reasoning to the tilted case. A tilted photograph is the case where the camera axis deviates only slightly and unintentionally from the nadir direction, consistent with option (B), which is therefore also true. Step 5: Summarize using the perpendicularity chain. Camera axis normal to the datum plane, the vertical case, implies photo plane parallel to the datum plane; camera axis measurably off-normal by design implies oblique; camera axis off the nadir line by a small unintentional amount implies tilted. This confirms (A) and (B) as correct and (C), (D) as incorrect.\[ \boxed{\text{(A) and (B)}} \]
