Which instrument helps determine magnetic north and an azimuth?

A compass is designed to determine magnetic north and provide an azimuth, which is the angle between the direction of an object and a reference direction, usually north. The compass works by using a magnetized needle that aligns itself with the Earth's magnetic field, indicating the direction of magnetic north. By knowing magnetic north, one can easily calculate bearings or directions to navigate.

In contrast, a hygrometer measures humidity, a gyroscope provides information about orientation and angular velocity, and a theodolite is used for measuring angles in horizontal and vertical planes, primarily for surveying purposes. While the theodolite can measure angles, it does not directly determine magnetic north; instead, it typically references true north based on the measurements taken. This distinct functionality of the compass makes it the appropriate choice for determining magnetic north and azimuth.