Abstract: A computer implemented method, program and system for determining the attitude of a vehicle from two sets of local frame and body frame reference vectors utilizing solution equations for Euler sequence angles associated with rotation of a vehicle about a local frame reference vector. In particular, the method, computer program and system determines the attitude at a rate amenable for real time system use in conjunction with a wide array of sensor input sources such as star tracking devices, and provides estimators for the error in the reference vectors usable for surveillance of sensory input quality by flight management systems.