MAGNETOMETER SURVEYS IN MINERAL EXPLORATION: A RELIABLE FIRST STEP Magnetometer surveys have been used for many years as an established and reliable first step in any mineral exploration effort, according to Burns in a telephone interview. A magnetometer is a passive sensor that measures variations in the Earth's magnetic field. The recorded data, depending on its quality, can provide insights into what lies beneath the surface. While terms like LiDAR, photogrammetry, and thermal imaging are oft