Abstract <p>Strapdown inertial navigation systems (SINS) are essential elements of control systems in various vehicles. Their accuracy defines the carrier’s capabilities of autonomous navigation, and, for the most part, its control system architecture. Instrumental errors of a navigation system are one of the critical factors affecting the precision of its sensors. Meanwhile, for a strapdown system, its navigation errors depend not only on the instrumental errors themselves but also on a particular combination of error components in conjunction with the trajectory of the carrier. In this article, we describe a method for the case of constant instrumental error model parameters that allows finding such a domain in the parameter space that ensures the circular position error is smaller than the predefined tolerance. The same approach enables identifying the most significant error sources.</p>