 A compass is one such device, one that measures the direction of an ambient magnetic field, in this case, the Earth's magnetic field.The first magnetometer capable of measuring the absolute magnetic intensity was invented by Carl Friedrich Gauss in 1833 and notable developments in the 19th century included the Hall effect, which is still widely used.Magnetometers are widely used for measuring the Earth's magnetic field, and in geophysical surveys, to detect magnetic anomalies of various types.