What is the main characteristic of the INS in terms of environmental operations?

The main characteristic of an Inertial Navigation System (INS) is its ability to function in a completely independent manner from external signals. This independence is critical because it allows the system to determine its position, orientation, and velocity using internal sensors, such as accelerometers and gyroscopes, without relying on external inputs like GPS or other navigational aids. This makes the INS highly useful in environments where external signals might be weak or unavailable, such as underwater or in space, where traditional navigation aids may not be effective.

By being unaffected by the operational environment, the INS provides reliable navigational data even in challenging conditions, ensuring that a vehicle or craft can continue to operate effectively.