Magnetic surveys are geophysical methods used to measure variations in the Earth's magnetic field. These surveys help identify subsurface geological features by detecting changes in magnetic properties caused by different rock types or mineral deposits. They are commonly used in mineral exploration, archaeology, and environmental studies. During a magnetic survey, specialized instruments, such as magnetometers, are employed to collect data over a specific area. The collected data is then analyzed to create magnetic maps, which can reveal important information about the Earth's structure and assist in locating resources like iron ore or gold.