NATS 1745 Lecture Notes - Lecture 3: Remote Sensing, Ground-Penetrating Radar, Heliacal Rising
12 Feb 2016
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Can detect iron, burnt soil, steel and rock types. Looks for changes in earth"s magnetic field ---points to structure change or object --- detect filled pits, ditches, post holes. Also used cesium magnetometer ---- ultra-sensitive -- if bacteria ate the posts in the henge, even that is picked up. Attached to atv"s: ground penetrating radar array. Sends radar pulses into the ground --- bounces back --- gives information about what lies beneath, how deep beneath, reveal hidden structure, bones. It takes multiple angles to reconstruct a 3d object. Sensors are pushed by hands or pulled by tractors. Allows using slightly different frequencies to find out what there is in multiple levels. Can reflect off buried artifacts, variations in soil types, etc: electromagnetic induction. Induction: changing magnetic field generates an electric current and vice versa. Emits magnetic field --- generates electric current in the objects underground. The electric current generates another magnetic field --- detects + gives information about the objects.
