Our goal is to have:
Autonomous GPS Guidance System.
Independent (back-up) Inertial Navigation System. (INS)

GPS is the modern way of guideance in the aviation world.

Inertial navigation systems (INS) are used since the second world war.
Those german V2 rockets, which hit london were guided by these systems.
The systems improved and now all components have to be very precise and reliable.
As a consequence, the costs for such a system are still very high (> 100'000 US$)
OOPS this is over our budget !!

The Attitude and Heading Reference Systems (AHRS) is a sub system of this INS.