In resection, how does landmark geometry affect accuracy?

• A. Closer landmarks always improve accuracy.
• B. Poorly spaced landmarks degrade accuracy due to angular geometry.
• C. Landmark geometry has no impact on accuracy.
• D. Fewer landmarks always yield higher accuracy.

Answer: (B)

In resection, accuracy depends on how the landmarks are spread around the observer—the angular geometry. If landmarks are poorly spaced, the directions from the camera to those points are too similar or nearly collinear, which makes the pose estimation ill-conditioned. When the angular separation is small, small measurement or image noise creates large errors in depth and orientation, so the overall accuracy suffers. Spreading landmarks across a wide range of directions provides more independent constraints and stabilizes the solution.

The other statements miss this geometric reality. Simply having landmarks closer together doesn’t guarantee better accuracy, and having fewer landmarks generally reduces information and accuracy.