On what basis is cruising altitude selected in Southern Domestic Airspace (SDA)?

Cruising altitude in Southern Domestic Airspace (SDA) is selected based on magnetic track. This alignment with magnetic track allows pilots to maintain a consistent altitude in relation to their intended path of flight, especially for en route operations.

The regulations specify that the altimeter settings should be adjusted, and cruising altitudes are assigned based on the magnetic track rather than magnetic heading or true heading. This is an important distinction, as magnetic track accounts for the curvature of the earth and magnetic variations, ensuring that aircraft maintain safe vertical separation.

Selecting cruising altitude based on magnetic track aids in standardization across general aviation and commercial operations, thus facilitating effective traffic management and enhancing overall safety in the airspace.