= Solution
Collect a \b[<magnetic survey>] along the traverse with a calibrated total-field magnetometer, recording time, accurately surveyed position and sensor height. Extend observations beyond the crater to establish the background, repeat stations or tie lines to test consistency, and use a stationary <base-station magnetometer> to monitor temporal field changes. Keep the instrument away from vehicles, fences and magnetic equipment; map unavoidable cultural sources rather than treating them as geological signals.
Correct instrument offsets and heading effects where applicable, remove measured diurnal variation, reject or separately treat magnetic-storm intervals, and subtract the appropriate large-scale <geomagnetic field> at the survey epoch. Level overlapping traverses and state whether a local regional trend has also been removed. Unlike gravity, there is no universal rock-independent Bouguer correction for magnetic topography: a <magnetic topographic effect> needs a model of terrain and <magnetization>.
Measure representative <magnetic susceptibility> and <remanent magnetization> on oriented rock samples to interpret the profile. Total field alone does not tell whether a contrast comes from induced or <remanent magnetization>, crater excavation, or strongly magnetic material in the infill.
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