Homologous points in photogrammetry — identifying corresponding pairs Which of the following pairs are homologous points (i.e., correspond to the same object point in the ground–image relationship)?
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APhoto principal point and ground principal point
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BPhoto isocentre and ground isocentre
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CPhoto plumb point and ground plumb point
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DAll of the above
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ENone of these
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:In photogrammetry, a “homologous” pair comprises an image-space point and its corresponding point defined in object space (ground) under the imaging geometry. Recognizing homologous feature pairs supports orientation, calibration, and quality control of aerial photographs.
Given Data / Assumptions:
- Standard definitions of principal point, isocentre, and plumb (nadir) point.
- Well-defined camera geometry and ground reference framework.
Concept / Approach:The photo principal point corresponds to the ground principal point; likewise, the photo isocentre corresponds to its ground counterpart; and the photo plumb point corresponds to the ground plumb point. Each pair refers to the same conceptual entity in image and ground spaces and is therefore homologous.
Step-by-Step Solution:
Match each photo-defined control point to its ground-defined counterpart.All listed pairs represent the same physical/geometry-based feature in their respective domains.Hence, choose “All of the above.”Verification / Alternative check:Orientation procedures treat these control points as conjugate entities when transforming between image and object spaces, confirming their homologous nature.
Why Other Options Are Wrong:
- Rejecting any single pair would contradict standard photogrammetric definitions.
Common Pitfalls:Confusing homologous points with conjugate image points between left and right photos; here, the pairing is between photo and ground, not between two photos.
Final Answer:All of the above