Difficulty: Medium
Correct Answer: 1, 3, 2, 4, 5
Explanation:
Introduction / Context:
Three-point resection fixes an unknown plane-table station by sighting three well-defined points already plotted on the sheet. Practical solutions (e.g., Lehmann’s method) refine an initial orientation until the small triangle of error collapses to a point.
Given Data / Assumptions:
Concept / Approach:
After rough orientation, rays are drawn back from the plotted points toward the ground objects. Imperfect orientation creates a small triangle of error where the rays fail to meet. Choosing a trial point within this triangle and applying equal rotations aligns plotted and ground directions; refining this removes the triangle and fixes the true station.
Step-by-Step Solution:
Verification / Alternative check:
Good geometry (well-spread controls) yields a tiny triangle and rapid convergence; poor geometry causes instability and large corrections.
Why Other Options Are Wrong:
They mix the order; the triangle appears only after rays are drawn, and choosing the trial point comes after recognizing the triangle.
Common Pitfalls:
Controls nearly collinear or acute geometry; these enlarge the triangle and degrade accuracy.
Final Answer:
1, 3, 2, 4, 5
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