5. Application example: GPSIRS positioning on board commercial aircraft

Commercial aircraft have been using inertial navigation systems for en-route positioning since the 1970s, and GPS since the mid-1990s. In fact, they are equipped with ADIRUs (Air Data Inertial Reference Units): the inertial solution provides positioning in the horizontal plane only, while vertical positioning is provided by a baro-altimeter, which is also used to recalibrate inertial vertical acceleration and velocity within the platform.

There are three main types of baro-IRS/GPS hybridization on board commercial aircraft:

• Honeywell's first loose hybridization solution;

• two close-hybridization solutions: one from Honeywell, the other from Northrop Grumman.

These three solutions are therefore based on the assumption that the information provided...