4. Inertial hybridization

The combination of two different systems with complementary characteristics makes it possible to overcome the shortcomings of each. This is particularly true of the GPS system, which is accurate in the long term but can be subject to noise and momentary measurement shortfalls, and another positioning method based on completely different principles, inertia, whose short-term accuracy is very good but which drifts over time.

In the coupling between an inertial system and GPS, the radio system readjusts the inertia and prevents it from drifting; the inertia provides measurement continuity, supplements GPS in the event of satellite signal obstruction, and smoothes the radio measurement in the event of multiple paths.

The inertial system can be of very different classes:

• gimbaled inertial unit where...