Inertial Navigation System (INS) refers to a system based on dead reckoning, that integrates several sensors in order to calculate your position.

If you know your previous position,lets say 1 second ago, and you know your speed and direction then you can determine where you are now.

An inertial reference system, in terms of geodesy refers to a coordinate system that does not move with the Earth, it has its axis oriented to fix points outside of Earth. Inertial Reference coordinate systems are used for position of bodies outside of Earth

the disadvantages is it need to give data before flight

Andrew L. Gordan has written:

'Optical alignment of Centaur's inertial guidance system' -- subject(s): Inertial navigation (Astronautics)

Frank Coffman Bell has written:

'Schuler's principle and inertial navigation' -- subject(s): Gravitation, Inertial navigation (Aeronautics)