With reference to inertial navigation systems, a TAS input is:

Inertial navigation systems (INS) rely on various inputs to maintain accurate positioning and navigation data. One critical piece of information for these systems is the True Airspeed (TAS). When determining wind calculations, a TAS input is essential for providing a Wind Vector (W/V) readout. The wind vector indicates both the direction and speed of wind relative to the aircraft's flight path.

The inclusion of TAS allows the system to calculate how the wind affects the aircraft's course and speed over the ground, facilitating more accurate navigation and performance assessments. This becomes particularly important during flight as it enables pilots to account for various wind conditions.

While other navigation methods like polar or rhumb line navigation might utilize different principles or calculations, they do not specifically require the TAS input for their primary function. Thus, the necessity of a TAS input in providing a W/V readout solidifies its role in enhancing the efficacy of inertial navigation systems.