You may have noticed a helicopter flying over Sault Ste. Marie the last few days. There’s nothing strange about that, but there is something weird about this one.
The helicopter spotted yesterday in the western sections of the city seemed to be dragging something underneath it, what appears to be a net of some kind.
Turns out, it was likely an airborne electromagnetic (AEM) survey .
An AEM is used to measure natural variations in the electrical properties of soil, rocks and water. Surveys are conducted by government agencies and companies using a light aircraft or helicopter operated by a specialist contractor.
The loop is about 60-feet (20 m) in diameter and weighs about 1000 pounds (450 kg). It is suspended about 100 feet (35 m) below a helicopter, which flies about 200 feet (65 m) above the ground. The helicopter travels an average of 45-75 mph (70 – 120 kph) in closely spaced parallel lines across the area to be mapped.
Some of things we discovered from the web about AEM include;
AEM detects geological changes and moisture variations beneath the earth’s surface.
Most systems generate primary EM fields by using a loop transmitter; conducting coils are used as antenna to measure the secondary magnetic field caused by conductive inhomogeneities in the ground.
We can’t confirm what ares of Sault Ste. Marie were mapped, if any, but in case you may look up and see a loop transmitter underneath a flying helicopter, now you know.