Geophysical method

AMP

Magnetometry

Soil carries the magnetic memory of whatever heated it, disturbed it or crossed it. That memory can be read without emitting anything.

How it works.

The method is entirely passive: it emits nothing. It measures the minute variations in the Earth's magnetic field caused by elements in the shallow subsurface, by reading the gradient between two stacked sensors.

Two families of object stand out clearly. Iron, through its own magnetisation. And fired earth — kilns, hearths, brick — whose cooling locked in a remanent magnetisation. Backfilled pits also emerge, their fill being more magnetic than the surrounding ground.

  • Method

    Passive, no emission

  • Quantity

    Magnetic gradient

  • Sensitivity

    Fired earth, ferrous objects

  • Deliverable

    Magnetic map

What it reveals.

  • Kilns, hearths and fired structures
  • Backfilled pits, silos and post holes
  • Ferrous objects and metal pipework
  • Buried metal tanks
  • Unexploded ordnance and pyrotechnic risk

Where we use it.

Indispensable in archaeology, and decisive wherever a site may hold metal.

Methods

A site to survey magnetically?

Let's talk extent, context and detection objectives.

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