The results of an evaluation of the computational errors for conventional, restrained, strapdown sensor mechanizations are presented. The analytic models of the computational errors (truncation, word length, integration scheme, integration interval, and sensor output resolution) presented were developed through detailed digital simulation of the navigation sensors and different data processing schemes. (Both the processes of computing vehicle attitude and transforming the accelerometer data from the vehicle to the inertial frame are considered.) These error models demonstrate the techniques by which computational processes can be properly designed for different applications and the magnitude of the computational errors controlled. Test data obtained during the centrifuge testing of a strapdown system are also presented, and demonstrate good agreement with the attitude computational error models. Of additional significance are the development and presentation herein of a gyro data processing technique that eliminates the commutativity error and permits the use of higher-order integration schemes for determining attitude; a fourth-order scheme is presented as an example.