Inertial Navigation Systems
 

Folks,

I have read that an INS system must be initialised before flight. Presumably this is so that the aircraft knows where it is starting from. But how is it done? Is GPS used? And why does it take some time - apparently up to ten minutes. Just curious.

You may find this recent thread relevant.

The Airport Gates( Aircraft Parking bays on the ramp) are surveyed to a high degree of accuracy for there Lat and Long co-ordinates.
This information is then loaded and stored in the FMS and this can be either transferred into the Air data inertial reference system or entered manually.
The IRS/INS needs this to calibrate its position, but I read somewhere it really can do this without any input, so the co-ordiates are entered to get the whole process moving faster.

Also while the whole alignment process is in progress the aircraft must not be moved, Aircraft have been stuck on taxiways due to this essential procedure being forgotten.

I hope this helps!