ABSTRACT This paper provides an overview of assorted analysis techniques associated with strapdown inertial navigation systems. The process of strapdown system algorithm validation is discussed. Closed-form analytical simulator drivers are described that can be used to exercise/validate various strapdown algorithm groups. Analytical methods are presented for analyzing the accuracy of strapdown attitude, velocity and position integration algorithms (including position algorithm folding effects) as a function of algorithm repetition rate and system vibration inputs. Included is a description of a simplified analytical model that can be used to translate system vibrations into inertial sensor inputs as a function of sensor assembly mounting imbalances. Strapdown system static drift and rotation test procedures/equations are described for determining strapdown sensor calibration coefficients. The paper overviews Kalman filter design and covariance analysis techniques and describes a general procedure for validating aided strapdown system Kalman filter configurations. Finally, the paper discusses the general process of system integration testing to verify that system functional operations are performed properly and accurately by all hardware, software and interface elements. COORDINATE FRAMES As used in this paper, a coordinate frame is an analytical abstraction defined by three mutually perpendicular unit vectors. A coordinate frame can be visualized as a set of three perpendicular lines (axes) passing through a common point (origin) with the unit vectors emanating from the origin along the axes. In this paper, the physical position of each coordinate frame's origin is arbitrary. The principal coordinate frames utilized are the following: B Frame = "Body" coordinate frame parallel to strapdown inertial sensor axes. 1 N Frame = "Navigation" coordinate frame having Z axis parallel to the upward vertical at the local position location. A "wander azimuth" N Frame has the horizontal X, Y axes rotating relative to non-rotating inertial space at the local vertical component of earth's rate about the Z axis. A "free azimuth" N Frame would have zero inertial rotation rate of the X, Y axes around the Z axis. A "geographic" N Frame would have the X, Y axes rotated around Z to maintain the Y axis parallel to local true north. E Frame = "Earth" referenced coordinate frame with fixed angular geometry relative to the earth. I Frame = "Inertial" non-rotating coordinate frame. NOTATION V = Vector without specific coordinate frame designation. A vector is a parameter that has length and direction. The vectors used in the paper are classified as "free vectors", hence, have no preferred location in coordinate frames in which they are analytically described
