Homologous points in stereophotogrammetry In aerial photogrammetry, what is meant by a homologous point?

Introduction / Context:
“Homologous points” are fundamental to stereoscopy and photogrammetric measurements of height and plan position. Matching these points accurately across overlapping photos enables parallax measurement and 3D reconstruction.

Given Data / Assumptions:

• Stereo pair: two overlapping aerial photographs of the same terrain.
• Each ground point ideally appears on both photos within the overlap region.
• Interior and exterior orientation are used to relate image points to ground coordinates.

Concept / Approach:
A homologous point is the corresponding image of the same ground object on each of the two photographs that form the stereoscopic pair. Identifying homologous points allows the calculation of parallax differences, which are then used to derive elevations and to build models in analog or digital stereo plotters.

Step-by-Step Solution:
Define correspondence: the two image points represent one ground point captured from two camera stations.Use their measured parallax to compute relative height or to perform bundle adjustment.Therefore option (a) correctly captures the definition.

Verification / Alternative check:
In digital photogrammetry, feature matching (e.g., tie points) operationalizes the search for homologous points to densify point clouds for surface reconstruction.

Why Other Options Are Wrong:

• (b), (c), (d) are special points on a single photo, not a pairwise correspondence.
• (e) Nodal points belong to lens geometry and are not “homologous points”.

Common Pitfalls:
Confusing homologous points (photo-to-photo) with the relation between a ground point and its single photo image.

Final Answer:
The image of the same ground point appearing on each photograph of a stereo pair