Final answer:
Long term references for an AHRS are created using inertial sensors, magnetic sensors, and sometimes GPS data, which are processed by algorithms like the Kalman filter to generate stable and accurate orientation information.
Step-by-step explanation:
Long term references for an AHRS (Attitude and Heading Reference System) are typically generated using a combination of sensors and algorithms. The most common method involves the use of inertial sensors, such as accelerometers and gyroscopes, to continuously calculate the orientation of an object in space. These measurements are subject to drift over time due to sensor errors. To mitigate this, many systems incorporate magnetic sensors (magnetometers) that provide heading references relative to the Earth's magnetic field, and sometimes GPS data is used to provide additional positional references. Sensor data is then processed by an algorithm, often a form of a Kalman filter, which combines the sensor inputs to produce a stable and accurate long-term reference for attitude and heading.