When the metal detecting hobby was in its infancy, detector would beep out a signal, but the hunter couldn't tell what type of metal had been found. After digging, the object might turn out to be a gold relic or just an old bottle cap. In 2010, metal detectors can discriminate between different metals and inform a hunter exactly what is below the surface.
Metals Discrimination
Metals discrimination is a key feature of modern metal detectors. Different metals have different electromagnetic qualities. Metals detectors send electromagnetic waves down, and the metals return a signal based upon their magnetic characteristics. The ability to differentiate between metals is called discrimination.
Calibration
Metals detectors have a calibration feature called ground balance. All soils contain some iron or other metallic minerals. If this were not accounted for, metal detectors would always return a positive signal, since the metal detector reads all metals. The metal content of the soil is calibrated out of the reading by a knob that adjusts for ground balance. A sequence of steps is required for proper adjustment and calibration should be set for every soil type.
Radar
Ground penetrating radar gives a true underground picture of objects. An electromagnetic wave is shot into the ground, and it reflects back any anomalies. In 2006, research funded by the Japan Science and Technology Agency investigated mounting GPR on robotic cars for land mine detection. The conclusion was GPR had a confidence rating of about 80 percent. In 2009 Archaeologists at Georgia Southern University used GPR to investigate Camp Lawton, a Civil War-era POW camp.
Old Versus New
In 2010, metal detectors have internal microprocessors, which allow the hunter to set the detector to "beep" only on specific metals, such as gold, iron or metal coins.
Before microprocessors, metal detectors could not inform you if the object was iron or non-ferrous. Today, a metal detector can inform of the composition of the metal, so you don't waste your time digging for objects with no monetary value. With microprocessors and ground penetrating radar, a metal detector is able to give you a rudimentary picture of what an object looks like, and how deep it is beneath the surface.
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