A land magnetic survey was carried out along a profile length of 500 m with an inter-station spacing of 5 m over a buried ore body. The optimum width of the body that can be best resolved is __________ m (answer in integer).
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Correct Answer: 10
Solution and Explanation
In any profile survey (magnetic, gravity, resistivity, etc.), the station spacing \(\Delta x\) sets a limit on the smallest feature that can be reliably picked up, in the same way a sampling interval limits the highest frequency recoverable in time-series work.
Step 1: Treat the station spacing as a spatial sampling interval.
Here \(\Delta x = 5\) m. By the spatial version of the sampling (Nyquist) theorem, at least two independent readings must fall across the width of a target for its anomaly to be resolved without aliasing - a single station only tells you a value exists, not the shape or width of the source causing it.
Step 2: Apply the two-samples-per-target rule.
Optimum (minimum reliably resolvable) width, \(w_{opt} = 2\Delta x = 2 \times 5 = 10\) m.
Step 3: Note what the profile length is for.
The 500 m profile length only fixes how many stations exist along the line (\(500/5 + 1 = 101\) stations); it does not enter the resolution calculation, since resolution is governed by the sampling interval, not the total survey length.
So the ore body's optimum resolvable width is \(\boxed{10\ \text{m}}\), matching the key.
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