Air Data Computer
An air data computer (ADC) is an essential avionics component found in modern glass cockpits. This computer, rather than individual instruments, can determine the calibrated airspeed, Mach number, altitude, and altitude trend from input data from sensors such as an aircraft's pitot-static system, gyroscopes, GPS and accelerometers. In some very high speed aircraft such as the Space Shuttle, equivalent airspeed is calculated instead of calibrated airspeed.
Air data computers usually also have an input of total air temperature. This enables computation of static air temperature and true airspeed.
In Airbus aircraft the air data computer is combined with altitude, heading and navigation sources in a single unit known as the Air Data Inertial Reference Unit (ADIRU). This has now been replaced by Global Navigation Air Data Inertial Reference System (GNADIRS).