What feature makes the Inertial Navigation System impervious to enemy countermeasures?

The feature that makes the Inertial Navigation System (INS) impervious to enemy countermeasures is its self-contained operation. An INS operates independently, using internal sensors to calculate the position, orientation, and velocity of a moving object without relying on external references or signals. This means that it is not subject to jamming or other forms of interference that could be used by adversaries to disrupt navigation systems that depend on external signals, such as GPS.

This self-contained nature provides a significant advantage in environments where external signals might be compromised, ensuring that the system can continue to function accurately and reliably, even in hostile conditions. By maintaining a constant awareness of its position through internal computations, the INS provides a robust solution for navigation that is not vulnerable to countermeasures aimed at disrupting external signals.