Which device is utilized to measure the magnetic field surrounding an aircraft?

The device that measures the magnetic field surrounding an aircraft is a magnetometer. This instrument detects and measures the strength and direction of magnetic fields, which is crucial for various applications in aviation. It helps pilots and navigators determine their orientation relative to the Earth's magnetic field, assisting in navigation and control of the aircraft. Magnetometers are often used in conjunction with other navigation systems to enhance accuracy and reliability.

In the context of aircraft, understanding the magnetic field is important for heading information and compass readings. The magnetometer's output can be used to correct any errors and provide pilots with precise navigational data, which is vital for safe and efficient flight operations.

Other devices listed serve different purposes. A barometer measures atmospheric pressure, which is important for altitude and weather prediction; an altimeter specifically measures altitude by assessing changes in air pressure; and a gyroscope provides information on the aircraft's orientation and helps maintain stability. Each of these instruments is essential in aviation, but only the magnetometer is designed specifically for measuring magnetic fields.