The problem of autonomous determination using primary and/or secondary data of a strapdown inertial navigation system of two events is considered: the beginning and end of the movement of an object, and, as a consequence, determining the intervals of the immobility of the object. The task makes sense for airfield-based objects, when there are no other motion sensors, and also when the object can stop for an indefinite time when the object is taxiing along the airfield’s lanes. Detection of immobility intervals allows applying a zero velocity correction of the strapdown inertial navigation system or ZUPT-correction (Zero velocity UPdaTe), which is important for the subsequent functioning of the strapdown inertial navigation system. Two approaches to the construction of algorithms for detecting the start and stopping of the movement of an object are described. The first is based on the use of the primary information of a strapdown inertial navigation system, i.e., the readings of inertial sensors (accelerometers, angular velocity sensors); and the second, on the use of secondary information (positional, speed, angular data of the autonomous inertial calculation). Both approaches are based on heuristic criteria obtained empirically when processing data from strapdown inertial navigation systems and taking into account the specifics of the problem. The results of testing the developed algorithms on the experimental data for strapdown inertial navigation systems (SINS) of the navigation accuracy class are presented.