ABSTRACT
A fundamental requirement of inertial navigation
is the initial alignment process; this is required to
determine a local vertical and direction of true
north. Alignment must be carried out with the
aircraft on the ground and stationary. (Note that
in certain cases, e.g. on the flight deck of an
aircraft carrier, alignment has to be accomplished
whilst the aircraft is moving. In this case, an
external reference is required, e.g. the carrier’s
own inertial navigation system.) Systems using an
electromechanical gimballed platform need this
time for the gyros to level the platform with
respect to the local vertical and align the platform
in the direction of true north. For strap-down
systems, there is no platform as such; however,
the system still needs to establish a local attitude
reference and direction of true north for
navigation purposes.
