In flight Alignment of Low Grade Strapdown Navigation System

This paper presents In-motion alignment, the common name to all the initialization methods which are employed during the motion of the system. In this case, as the system undergoes an arbitrary movement during initialization, it is not possible to assign initial values without an aid of some external reference source. Therefore, the essential part of in-motion alignment is the process of transfer of navigation information from a reference source (in the present case, the MINS)to the navigation system (SINS) which has to undergo alignment with MINS navigation information. Hence, this method of alignment is referred to as Transfer Alignment (TA), aligning Slave Inertial Navigation System (SINS) with Master Inertial Navigation System(MINS) as reference when they are on a moving platform. SINS is initialized with MINS attitude for estimating the misalignment between master & slave, other information such as initial velocity, initial position of SINS are initialized with present position & present velocity of MINS.A nine state Kalman Filter is designed to find the estimates of attitude misalignment between master and slave, the sensor biases and its observables are attitude difference vectors.