[1] Before the advent of sophisticated flight management systems, Carousel IV allowed pilots to automate navigation of an aircraft along a series of waypoints that they entered via a control console in the cockpit.
The system used spinning mass gyroscopes and proof-mass accelerometers to measure movement from the start point.
An involved calculation followed by sampling those sensors to determine a current position relative to the surface of the Earth.
The Carousel IV system derives its name from the fact that the inertial reference platform was rotated 360° every 60 seconds as a technique to reduce drift and increase accuracy by countering systematic errors.
The elevated temperature was maintained whenever the system was switched on in either the 'Standby', 'Align', 'Navigate' or 'Attitude' mode, as selected on the Control Display Unit (CDU).