= Solution
Lay out a surveyed grid extending beyond the possible burial area into unaffected ground. Use closely spaced parallel traverses with measurements along each line; spacing should resolve a car-scale <magnetic anomaly>, with a finer grid over any candidate. For a shallow car, a pilot survey with roughly metre-scale spacing is a sensible starting point, refined according to anomaly width rather than treated as a universal prescription. Record position, time, sensor height, repeat readings and any nearby interference. Cross-lines and repeat stations check reproducibility. Maintain a constant sensor height on a nonmagnetic staff and remove magnetic items from the operator; map fences, gates, pipes, buildings and vehicles before interpreting an anomaly.
Operate a synchronized stationary <base-station magnetometer> in quiet ground while the rover surveys, or make frequent base returns if a second instrument is unavailable. A <total-field magnetic anomaly> is the corrected field magnitude minus a specified background:
$$
\Delta T(\mathbf x)=F_{\mathrm{corrected}}(\mathbf x)-F_{\mathrm{background}}(\mathbf x).
$$
For a field-sized target, a local background estimated away from the car is often sufficient. A larger regional survey may subtract the <International Geomagnetic Reference Field> and an independently justified regional trend. Do not remove the car's broad anomaly by overfitting that trend.
Correct rover observations for time-varying <geomagnetic field> using the base record, for example $F_c(\mathbf x,t)=F_r(\mathbf x,t)-[F_b(t)-F_b(t_0)]$. Check instrument offsets and tie-line differences, reject disturbed or poor-quality readings, and allow for differing sensor heights. Preserve localized target signals when interpolating a contour map or comparing with a <magnetic dipole> model. There are no compulsory gravity-style free-air or <Bouguer gravity anomaly> reductions for this magnetic search.
Postpone surveying during a <geomagnetic storm> or rapid irregular magnetic variation, when base correction may be inadequate. Avoid periods of moving farm machinery or electrical interference, and recognize that strong permanent cultural interference or highly magnetic host <rock> may make this particular method unsuitable. Ordinary cloud cover or darkness does not prevent a <magnetic survey>.<G-857 Memory-Mag operation manual by Geometrics>[“Magnetic Environment” and survey/base-station operation: magnetic cleanliness, spatial gradients, and time variation.]{ref}
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