What is an accelerometer?
An accelerometer measures proper acceleration. This is the acceleration it experiences relative to free-fall and is the acceleration felt by people and objects. Put another way, at any point in space-time the equivalence principle guarantees the existence of a local inertial frame, and an accelerometer measures the acceleration relative to that frame. Such accelerations are popularly measured in terms of g-force, or more precisely in terms of m/s².
What is a gyroscope?
A Gyroscope is a physical sensor that detects and measures the angular motion of an object relative to an inertial reference frame. The unique feature of gyroscopes is the ability to measure the absolute motion of an object without any external infrastructure or reference signals.
What is a magnetometer?
A magnetometer is a measuring sensor used to measure the strength or direction of magnetic fields in order to provide bearing.
What is MEMS Technology?
MEMS are Micro Electro-Mechanical Systems that integrate mechanical elements, sensors, actuators, and electronics located on a silicon substrate level. This technology enables miniature devices, and MEMS have proven to be a key enabling technology for developments in areas such as transportation, telecommunications and health care. MEMS sensors are now also widely used in consumer grade applications, such as smart-phones and gaming devices, but there is also a large market for higher quality MEMS devices, developed for automotive, aerospace and other applications.
Other advantages include small size, lower power consumption, lower cost, increased reliability and robustness.
What is an optical gyroscope (RLG and FOG)?
An optical gyroscope (Ring Laser Gyroscope and Fiber Optic Gyroscope) determines the angular rate of the system using the "Sagnac effect". Two light signals are emitted from opposite direction into an optic loop. If this loop is subject to rotation, then the light will be faster to travel one way than the other. By measuring this time difference we can estimate the rotational speed.
FOG are commonly assumed to be more accurate than MEMS gyroscopes, but nowadays high quality MEMS sensors achieve similar or better accuracy than many FOG sensors.